Method and Apparatus for Fabricating Fibers and Microstructures from Disparate Molar Mass Precursors

ABSTRACT

The disclosed methods and apparatus improve the fabrication of solid fibers and microstructures. In many embodiments, the fabrication is from gaseous, solid, semi-solid, liquid, critical, and supercritical mixtures using one or more low molar mass precursor(s), in combination with one or more high molar mass precursor(s). The methods and systems generally employ the thermal diffusion/Soret effect to concentrate the low molar mass precursor at a reaction zone, where the presence of the high molar mass precursor contributes to this concentration, and may also contribute to the reaction and insulate the reaction zone, thereby achieving higher fiber growth rates and/or reduced energy/heat expenditures together with reduced homogeneous nucleation. In some embodiments, the invention also relates to the permanent or semi-permanent recording and/or reading of information on or within fabricated fibers and microstructures. In some embodiments, the invention also relates to the fabrication of certain functionally-shaped fibers and microstructures. In some embodiments, the invention may also utilize laser beam profiling to enhance fiber and microstructure fabrication.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims priority to, and thebenefit of, U.S. application Ser. No. 16/165,535 titled “Method andApparatus for Fabricating Fibers and Microstructures from DisparateMolar Mass Precursors,” filed Oct. 19, 2018 (now U.S. Pat. No.10,683,574), which was a continuation of U.S. application Ser. No.14/827,752 titled “Method and Apparatus for Fabricating Fibers andMicrostructures from Disparate Molar Mass Precursors,” filed Aug. 17,2015 (now U.S. Pat. No. 10,167,555) and claimed priority to U.S.application Ser. No. 62/038,705 titled “Method and Apparatus ofFabricating Fibers from Disparate Molecular Mass Gaseous, Liquid,Critical and Supercritical Fluid Mixtures,” filed Aug. 18, 2014; U.S.application Ser. No. 62/074,703 titled “Doped Carbon Fibers andCarbon-Alloy Fibers and Method of Fabricating Thereof fromDisparate-Molecular Mass Gaseous-, Liquid, and Supercritical FluidMixtures,” filed Nov. 4, 2014; and U.S. application Ser. No. 62/074,739titled “Method and Apparatus for Recording Information on ModulatedFibers and Textiles and Device for Reading Same,” filed Nov. 4, 2014,the entire contents of which are herein incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

N/A

BACKGROUND OF THE INVENTION Field of the Invention

The present invention is in the technical field of fiber andmicrostructure fabrication. In some embodiments, the invention alsorelates to the permanent or semi-permanent recording and/or reading ofinformation on or within fibers and microstructures. In someembodiments, the invention also relates to the production of certainfunctionally-shaped and engineered short fiber and microstructurematerials. In some embodiments, the invention may also utilize laserbeam profiling to enhance fiber and microstructure fabrication.

In some aspects, this invention generally relates to production offibers that are commonly used to reinforce composite materials.Frequently, short strands of fiber are cut from longer rolls of fiber,wire, or rolled strips to predetermined lengths, and these are thenadded to composite matrix materials in random or ordered arrangements.These fibers are known as “chopped fiber” in the industry and are usedin a broad range of applications, from carbon-fiber reinforced polymersto sprayed-on metallic-fiber-reinforced insulation, to polymer-fiberreinforced concretes. In the composites industry, long strands of fiberare also spooled/joined into tow or ropes, which can then be used tocreate “fiber layups” and reinforce composite materials.

Very often, fibers provide increased strength to a composite material,while a surrounding matrix material possesses complementary properties.The overall strength of a composite material depends on both the fiberand matrix properties, but usually strength is compromised when thefibers can slip excessively relative to the matrix. Thus, one of thegreatest challenges associated with fiber-reinforcement of composites isoptimizing the “pull-out” strength of fibers within a matrix material.Traditionally, this has been done by: (1) increasing the adhesion orbonding strength at the interface between the fibers and matrixmaterial, or (2) increasing the surface area for contact between the twomaterials.

However, the concept of optimal fibers whose shapes are engineered tominimize pull-out while allowing the composite to remain flexible andtough is essentially absent from existing techniques. One reason forthis is simply that current manufacturing methods presume that the rawfiber or wire-based materials are derived from drawing the fibermaterial through dies; in the case of metallic strip, they are often cutfrom rolled metal sheeting. For many materials, it is difficult tomodify the cross-section of fibers dynamically using dies or rollingprocesses. Thus carbon-fiber manufacturers largely produce circularcross-section carbon fiber, and metallic fiber is often chopped fromcylindrical wire—all with constant cross-sections. Of course,ductile/metallic wire/strip can be rolled, indented, or bentmechanically to change its shape, but this is not practical for manyhigher strength (often brittle) materials that are desired forhigh-performance composites, such as carbon, silicon carbide, siliconnitride, boron, or boron nitride, etc. Forming processes increase theoverall expense of the process and are usually limited in the potentialgeometries that can be created. Thus, a method of modulating thecross-section versus length of reinforcing fibers is very desirable,especially when optimal reinforcing geometries can be created.

Note that pull-out strength is not the only parameter that must beoptimized for reinforcing fiber. In many situations, it is also usefulto have fibers that are designed to bend, flex, twist, etc. withoutfailure or delamination from the matrix. Creating fibers in shapes thatgive more isotropic properties are desired in many applications. Forexample, carbon fibers may have high tensile strengths in one directionwhile possessing poor compressive or shear strengths. This deriveslargely from the way in which they are processed from continuousstrands—which provides particular anisotropicmicrostructures/orientations along the axis of the fiber. However,changing the nominal geometric orientation of the fiber itself—intonon-linear geometries—can greatly improve the shear and flexureproperties of the resulting composite material. This is difficult toaccomplish through traditional fiber manufacturing methods.

Hyperbaric laser chemical vapor deposition has been traditionally usedwith simple Gaussian Laser Beam profiles to grow free-standing,three-dimensional fibers from a wide variety of materials. A Gaussianbeam profile is brightest in the center of the beam, and the intensitytails off radially with distance from the central axis of the beamaccording to:

I(r)=Io*Exp(−2r ² /wo ²)

When focused by a positive lens onto a surface, such a Gaussian beamgenerates a focal spot that also possesses this same Gaussiandistribution. Thus, when fibers are grown by HP-LCVD using a Gaussianbeam, the fiber is heated most at the center of the fiber, but theabsorbed energy drops radially. Provided the thermal conductivity of thefiber material is high, the fiber dimensions are small, and the growthrate slow, this absorbed thermal energy can conduct rapidly across thefiber tip, allowing the temperature profile within the reaction zone atthe fiber tip to be fairly uniform. However for moderate-to-low thermalconductivity materials, the center of the fiber is usually at a muchhigher temperatures than the fiber edges.

This creates several problems for rapid fiber growth: First, as thephase and composition of the material that is grown can depend stronglyon temperature, a non-uniform temperature distribution can create two ormore phases or compositions of materials in the fiber. For exampleduring the deposition of carbon fibers from ethylene, at least fourpossible material phases can be deposited: amorphous/fine-grainedcarbon, graphitic carbon, nodular carbon, and diamond-like carbon,depending on the reaction temperature. Thus, with a Gaussian laser beamat moderate laser powers, it is very common to grow carbon fibers thatpossess a graphitic carbon core, with an amorphous or fine-grainedcarbon coating. This is illustrated in FIG. 37(c). The graphitic coreoften consists of parabolic- or Gaussian-shaped graphite shells that arecentered on the fiber axis, and run outwards toward the fiber exterior.This material configuration provides strength radially, but is not verystrong along the fiber axis. This leaves the fibers with very littletensile strength along their primary axis—which is crucial for fiberreinforcement applications. To be most useful/competitive commercially,the carbon fibers grown by HP-LCVD should either be entirelyamorphous/glassy, or have graphitic planes running in the same directionas the fiber axis to add strength along that direction.

In addition, many desired fibers are binary or ternary compounds oralloys that are deposited using two or more precursors. Each precursorgenerally exhibits its own deposition kinetics and activation energy,and hence deposits differently vs. temperature than the otherprecursors. When a single-temperature is present, this is not generallyan issue, as the concentration of the gas-phase precursors cancompensate for the difference in deposition kinetics. However, in atemperature gradient, this will lead to a varying composition of thedeposit elements within the fiber. For a Gaussian beam, this means thata radial compositional gradient will exist for two or more precursors.Sometimes this can be of advantage (e.g. obtaining a protective coatingover a core material in a single-step). However, often a singlecomposition within the fiber is desired.

SUMMARY OF THE INVENTION

The invention generally relates to the synthesis of fibers from gaseous,solid, semi-solid, liquid, critical, and supercritical fluid mixtures,wherein the mixture is comprised of precursors with highly disparatemolar masses. In one of its simplest forms, it uses one low molar mass(“LMM”) precursor (e.g., silane), and one high molar mass (“HMM”)precursor (e.g., hexamethyldisilane), and employs the thermaldiffusion/Soret effect to concentrate the LMM precursor at the reactionzone where a fiber is growing. It is generally understood that the term“thermal diffusion” refers to the concentration effect, which can occurin gases, while the Soret effect is commonly understood as referring tothe concentration effect in liquids; throughout this document, we willuse the term “thermal diffusion” to refer to all instances of aconcentration effect, regardless of the state of the fluids. It shouldbe understood that the precursors do not necessarily have to be above orbelow a certain molar mass. Rather, the terms “LMM precursor” and “HMMprecursor” are used to contrast the relative molar masses of thedifferent precursors. The difference in molar mass of the precursorsneeds to be sufficient such that there is a substantive increase in theconcentration of the LMM precursor at the reaction zone relative to theremainder of the chamber volume. Thus, a LLM precursor may have arelatively “high” molar mass so long as it is sufficiently lower thanthe MINI precursor molar mass to achieve the desiredenhanced-concentration effect.

In a preferred embodiment, for “highly disparate molar masses,” themolar mass of the HMM precursor is at least 1.5 times greater than theLMM, and can be substantially greater, on the magnitude of 3 or moretimes greater. For example, in one specific embodiment using alkanes,the LMM precursor could be ethane, having an approximate mass of 30 amu(atomic mass unit), and the MINI precursor could be hexane, having anapproximate mass of 86 amu. In this example, the HMM is almost 3 timesthe mass of the LMM. In another example, methane might be used as theLMM, having an approximate mass of 16 amu, and hexadecane can be used asthe HMM, having an approximate mass of 226 amu. In this example, theMINI has a mass over 14 times higher than the LMM. For many precursors,the greater the difference in mass between the HMM and LMM, the morepositive effect on the fiber growth rates.

In this specification, we will assume that the term “molar mass” refersto the relative molar mass (m_(r)) of each precursor species (i.e.,relative to carbon-12), as determined by mass spectrometry or otherstandard methods of m_(r) determination. As the invention relies oncomparative measurements of substantively large differences in molarmass to obtain substantively enhanced growth rates of fibers, the use ofone method of molar mass determination versus another (or even differentdefinitions of molar mass) will be virtually negligible in practice tothe implementation of the invention. However, where the HMM or LMMspecies may be composed of a distribution of various species (e.g., forsome waxes, kerosene, gasoline, etc.), the meaning of “molar mass” inthis specification will be the mass average molar mass. Finally, itshould be noted that this invention applies to both naturally occurringand manmade isotopic distributions of the molar mass within eachprecursor species.

The HMM precursor, in addition, preferably possesses a lower massdiffusivity and lower thermal conductivity than the LMM precursor, andthe lower diffusivity and thermal conductivity of the HMM precursor thanthe LMM precursor, the better. This makes it possible for the MINIprecursor to insulate the reaction zone thermally, thereby lowering heattransfer from the reaction zone to the surrounding gases. The HMMprecursor will also provide a greater Peclet number (in general) andsupport greater convective flow than use of the LMM precursor on itsown. This enables more rapid convection within a small enclosingchamber, which in turn tends to decrease the size of the boundary layersurrounding the reaction zone, where diffusion across this boundarylayer is often the rate limiting step in the reaction. At the same time,the thermal diffusion effect helps to maintain at least a minimaldiffusive region over which a concentration gradient exists, allowingthe LMM precursor to be the maintained at high concentration at thereaction zone. Note that the HMM precursor can be an inert gas, whoseprimary function is to concentrate and insulate the LMM precursor.

Using the systems and methods described herein allows an LMM precursorto yield rapid fiber growth rates well beyond what is obtained throughthe use of the LMM precursor alone. In some cases, this has resulted ingrowth rates of one or two orders of magnitude beyond what is expectedfor a given laser power and reaction vessel chamber pressure. While thiseffect is not always observed for chemical vapor deposition (CVD)processes, it is apparent in microscale CVD processes where the heatingmeans for the reaction is localized.

Thus, in some embodiments, one aspect of this invention is thecombination of the thermal diffusion effect with the use of highlydisparate molar mass precursors so as to concentrate at least one of theprecursors at the reaction zone and increase the reaction rate and/orimprove properties of the resulting fibers. In addition, a means ofmaintaining the reaction zone within a region of space inside a reactionvessel, and translating or spooling the growing fibers at a rate similarto their growth rates so as to maintain the growing end of the fiberwithin the reaction zone, are disclosed that may help to maintain astable growth rate and properties of the fiber. Both short (chopped)fibers may be grown, as well as long spooled fibers. Methods aredisclosed for growing and collecting short (chopped) fiber, as well asspooling long fibers as individual strands or as tows or ropes. Duringthe growth of long fiber lengths, a fiber tensioner may also be providedto maintain the growing end of the fibers from moving excessively withinthis reaction zone—and so that the spooling of the fiber does notmisalign the fiber to the growth zone and interfere with their growth.There are a variety of ways to provide tension to a fiber known to thosein the industry. However, we are the first to develop a means oftensioning a fiber without holding the end that is growing, whileholding it centered in the reaction zone. We have developedelectrostatic, magnetic, fluidic, and/or mechanical centering/tensioningmeans that can be both passively and actively controlled.

In various embodiments discussed herein, a pyrolytic or photolitic(usually heterogeneous) decomposition of at least one precursor occurswithin the reaction zone. Decomposition of the LMM precursor may resultin the growth of a fiber; however, it is also possible to use an LMMprecursor that will react with the HMM precursor in the region of thereaction zone—where the LMM precursor would not yield a deposit of itsown accord. The decomposition reaction can be induced by either heat orlight, but is normally at least partially a thermally driven process;thus the thermal diffusion effect can be present, provided that theheating means is small and the surrounding vessel is substantiallycooler. In some embodiments, this invention enhances and controls thisthermal diffusion effect to produce more rapid and controlled growth offibers, which is of utility in reducing the production cost andincreasing the quality of fibers grown by this method.

The thermal gradient induced by a Gaussian beam can also induce thethermal diffusion effect. As discussed herein, this typically causes thelow molar mass (LMM) species which are in the gas phase to diffusetoward the center (hottest) portion of the gradient, while the heaviermolar mass (HMM) species diffuse away from the center. As theby-products of the HP-LCVD reaction are always less massive than theprecursors, this leads to a depletion of the precursors in the center ofthe reaction zone, effectively slowing the reaction rate along thecenter of the fiber axis (referred to as thermal diffusion growthsuppression (TDGS)). This can greatly reduce the production rate offibers by HP-LCVD.

Thus, in some embodiments, another aspect of the invention is that morethan one fiber can be grown in a controlled manner simultaneously. Thiscan be effected through the use of a plurality of heating sources, i.e.an array of heated spots or regions. For example, an array of focuslaser beams can be generated to initiate and continue fiber growth.However, other sources of heating are also possible, such as through theuse of induction heating of the fibers, use of an array of electricarcs, etc. As described further below, more than one heating means canbe used for each reaction zone, sometimes referred to herein as a“primary” heating means(s).

Now, it should be noted that temperature rises induced by the primaryheating means(s) can vary from spot to spot across an array of heatedspots, and this can produce undesirable variations in growth ratesand/or fiber properties from fiber to fiber. For example, in the use ofan array of focused laser beams there are often deviations in the spotto spot laser power of a few percent or more. In addition, variations inthe spot waist of each laser spot induce a large variation in thetemperature rise from spot to spot. Thus, even with precisiondiffractive optics or beam splitting, a laser spot array may yield avariation in peak surface temperature of over 20% from spot to spot.These variations must be either controlled electro-optically, orcompensated through other means, or the fiber growth rates will not besimilar and the fiber properties will vary. Where growth rates aresubstantially dissimilar, it becomes difficult to maintain a commongrowth front for many fibers at once. In this case, some fibers will lagbehind, and if the growth front is not tracked actively, they may ceasegrowing altogether once they leave their reaction zones.

Thus, in some embodiments, another aspect of this invention is that thethermal diffusion effect need not be induced solely by a primary heatingmeans, but can be induced and controlled by another source of heat(i.e., a “secondary” heating means), thereby providing another parameterwith which to drive and control the reaction rate and fiber properties.Where only the primary heating means is employed, the flow rate ofprecursors, pressure, and primary heating rate are the primarytools/parameters that can be used to control the reaction and fiberproperties (e.g. diameter, microstructure, etc.). If another heatingmeans is available to independently provide heat and control the thermaldiffusion gradient and size of the thermal diffusion region, animportant new tool is provided that can change the growth rate andproperties of the fibers independent of the primary heating means. Inaddition, whereas the primary heating means may be difficult orexpensive to control dynamically, such as in the use of electro-opticalmodulation of many laser beams, the secondary heating means can be verysimple—such as a resistive wire near, crossing, or around the reactionzone. Such a wire can be inexpensively heated by passing electriccurrent through it from an amplifier and a data acquisition system thatcontrols the temperature of the wire. Feedback of the thermal diffusiongradient and region size can be obtained optically with inexpensive CCDcameras, thereby allowing feedback control of the thermal diffusionregion by modulating electric current passing to the wire. With existingtechnology, this can be implemented in a simple manner that issubstantially less expensive than electro-optical modulation. This isespecially true when attempting to grow many fibers, such as hundreds orthousands of fibers, at once. To yield a commercially viable textile orfiber tow (i.e., untwisted bundle of continuous filaments or fibers)production system with thousands of fibers via laser-induced primaryheating means, where no secondary heating means is available, would bevery expensive, whereas actively controlling thousands of current loopsis relatively inexpensive and easy to implement. Thus, in someembodiments, the invention allows active control of a plurality ofthermal diffusion regions in order to control the growth and propertiesof fibers. Note that modulating the thermal diffusion region alsochanges the background temperature of the gases, which can alsoinfluence the growth rate.

Further, in some embodiments, this invention goes beyond controllingonly the thermal diffusion region within a given reaction zone, andprovides virtual conduits for flow of LMM precursors from their inletpoints within the vessel to each thermal diffusion region within the seaof HMM precursors. Heated wires can provide the flow conduits bycreating a long thermal diffusion region throughout the length of eachwire. In addition, in some embodiments, the invention provides a meansof modulating this flow of LMM precursors to each reaction zone byvarying the temperature of locations along the heated wires, therebyproviding a thermal diffusion valve that can increase or decrease flowof the LMM precursor to the reaction zone. For example, leads can branchoff the heated wire to draw current elsewhere and lower the currentthrough the remainder of the wire. Although traditional mass flowcontrollers and switching valves can be used, due to the length-scalesinvolved, the response time of one preferred method (using heated wiresas virtual flow conduits) is more rapid than that obtained throughtraditional mass flow controllers and switching valves that oftencontain a large latent volumes. Switching times on the order ofmilliseconds or less can be effected, allowing for rapid control ofproperties. These wires, if they are continued beyond the reaction zone,also provide a way to remove undesired byproducts from the reaction zoneand prevent them from mixing substantially with the surrounding gases.Pressure at the inlet point(s) of the virtual conduits can promote flowalong the conduits to and beyond the reaction zone.

During fiber growth from fluidic precursors, jets of heated gases (oftenby-products or precursor fragments) can sometimes be seen leaving aheated reaction zone. In one embodiment, heated wires emanating from thereaction zone(s) can channel these heated gases away from the reactionzone(s) and fiber tip, in desired directions, allowing more rapidgrowth.

In another embodiment, the wires/filaments/electrodes used to controlthe thermal diffusion region can also be charged relative to the fibersbeing grown to generate a discharge between the fibers and thewires/filaments/electrodes. Electrostatics and electromagnetics can beused to channel precursor(s), intermediate(s), and by-product speciesto/from the fiber and/or to thermal diffusion channels.

One aspect of this invention generally relates to the permanent orsemi-permanent recording of information on/within fibers and textilesusing the fabrication techniques and methodology described herein. Bymodulating the fibers' composition, geometry, or surface coatings,information can be recorded on/within these fibers. In addition, manyfibers can be grown at once, thereby enabling massively-parallelrecordings. The invention also provides a means of reading out thisinformation with a simple scanning apparatus.

The disclosed systems and methods can create archival recordingson/within high-temperature, oxidation-resistant materials, to preventdata loss from fire, flood, natural disasters, and/or electromagneticpulses. In addition, it provides a means to place random access memoryor data ubiquitously on a wide range of everyday products, such as in/onclothing, luggage, composite materials, etc. Information can also bewritten in such a way as to contain no non-linear junctions, magneticfilms, or metallic components that can be easily detected as electronicsor as recording media by sophisticated security systems. Data also canbe encrypted in a variety of physical manners, e.g. by switching betweenrecording modes (i.e. composition, geometry, properties, etc. overtime.) Without the proper reader, it would be very time consuming todecode.

This invention can be implemented in a variety of ways. The encoded datacan take many different forms—e.g. being represented within thecomposition, geometry, or physical/chemical properties of the fibers.

One aspect of the invention generally relates to the production ofcertain functionally-shaped and engineered short fiber materials in awide variety of shapes, configurations, orientations, and compositions.Another aspect of the invention relates to various systems and methodsto collect, recycle, and/or store manufactured fibers.

In another aspect, some embodiments of the invention utilize laser beamprofiling and control of the thermal diffusion region to enhance fiberand microstructure fabrication. In some embodiments, a reaction zone iscreated within a reaction vessel to decompose at least one precursor,the decomposition resulting in growth of a solid fiber in the reactionzone. The reaction zone is induced by a temperature regions beinggenerated by a heating means, and the temperature regions beingcontrolled to have specific induced temperature rises at surface vs.position and time at the surfaces of the solid fibers and within thesolid fibers. As such, the fibers can be grown having specificmicrostructural properties by controlling the induced temperature riseat surface.

BRIEF DESCRIPTION OF THE DRAWINGS

It should be noted that identical features in different drawings aregenerally shown with the same reference numeral. Various other objects,features and attendant advantages of the present invention will becomefully appreciated as the same becomes better understood when consideredin conjunction with the accompanying drawings.

FIG. 1 shows a thermal diffusion region, reaction zone, fiber, andpresence of LMM precursor and HMM precursor of one embodiment of theinvention.

FIG. 2 is one embodiment of the invention showing an array of thermaldiffusion zones, reaction zones, and fibers, together with fibertensioners and spooling device/mandrel.

FIG. 3 is one embodiment of the invention showing precursors flowedco-axially toward the reaction (or growth) zone.

FIG. 4 is one embodiment of the invention showing precursors flowed inplanar sheets toward the reaction (or growth) zones and an array offibers.

FIG. 5 is one embodiment of the invention depicting a two-phase (e.g. agas+liquid) system, having two thermal diffusion regions around eachfiber.

FIG. 6 is one embodiment of the invention depicting a two-phase (e.g.fluid+fluid/solid) system, having two thermal diffusion regions aroundeach fiber.

FIG. 7(a) shows one embodiment of the invention using a solid source ofHMM precursor.

FIG. 7(b) shows one embodiment of the invention using a liquid source ofHMM precursor.

FIG. 8(a) shows one embodiment of the invention using a primary heatingmeans and secondary heating means, namely a wire, having a partial loop.

FIG. 8(b) shows one embodiment of the invention using a primary heatingmeans and secondary heating means, namely a wire, having coils.

FIG. 9(a) shows one embodiment of the invention using a wire near or infront of an array of growing fibers.

FIG. 9(b) shows one embodiment of the invention using a wire manifoldand individual wires that can be modulated.

FIG. 10 shows one embodiment of the invention having a series of wiresnear or in front of a fiber.

FIG. 11 shows a flow diagram of one embodiment of the invention.

FIG. 12 is a graph showing the growth rate chart of a particularembodiment of the invention using methane as the LMM precursor andvarious more massive hydrocarbon HMM precursors at different LMM:HMMpartial pressures.

FIG. 13 is a graph showing the growth rate chart of a particularembodiment of the invention using methane as the LMM precursor and Xenon(inert gas) as the HMM precursor, at different pressures.

FIG. 14 shows expected thermal diffusion region separation graphs forgases for different geometries.

FIG. 15 shows expected thermal diffusion region separation graphs forliquids for different geometries.

FIG. 16 shows one embodiment of the invention using a baffle.

FIG. 17 is a graph showing the axial growth rate of carbon fibers usingmethane as the precursor, at different pressures.

FIG. 18 shows a graph depicting thermal diffusion region separations bymass difference.

FIG. 19 is a table of likely combinations of different material statesthat may be used in various embodiments of the invention.

FIGS. 20 (a)-(c) show three embodiments of the invention for encodinginformation in or on fibers.

FIG. 21 shows one embodiment of the invention using a laser as theprimary heating means and a secondary heating means (wire) to create afiber where the composition of the fibers is modulated along the lengthsof fibers to record information.

FIG. 22 shows one embodiment of the invention using a laser as theprimary heating means to create a fiber where the composition of thefibers is modulated along the length of the fibers to recordinformation.

FIG. 23 shows one embodiment of the invention using a laser as theprimary heating means and a laser as the secondary heating means tocreate a fiber where the composition of the fibers is modulated alongthe length of the fibers to record information.

FIG. 24 shows one embodiment of the invention using a laser as theprimary heating means and a secondary heating means using high pressuredischarge heating with an electrode to create a fiber where thecomposition of the fibers is modulated along the length of the fibers torecord information.

FIG. 25 shows one embodiment for a system for reading fiber states.

FIGS. 26(a)-(m) show a variety of different fiber shapes andconfigurations that can be manufactured using the disclosed systems andmethods (modulated cross-sections/profiles).

FIGS. 27(a)-(k) show additional fiber shapes and configurations that canbe manufactured using the disclosed systems and methods(various/variable cross-sectional shapes).

FIGS. 28(a)-(l) show additional fiber shapes and configurations that canbe manufactured using the disclosed systems and methods (non-linearorientations and complex examples).

FIG. 29 shows an example of one embodiment showing a combination ofprofiles, shapes, and geometric orientations of a fiber within a matrix.

FIG. 30 shows a smooth fiber with local smoothness <100 nm per 5microns.

FIGS. 31(a)-(c) show material blends and anisotropic blends inaccordance with one embodiment of the invention.

FIG. 32 shows a branched fiber in accordance with one embodiment of theinvention.

FIGS. 33(a)-(b) show zigzag-shaped fibers in accordance with oneembodiment of the invention.

FIGS. 34(a)-(d) show various embodiments of a fiber manufacturing andcollecting systems.

FIG. 35 shows a flexible substrate rolled up with fibers in accordancewith one embodiment of the invention.

FIG. 36 shows an example of a circular beam profile (a circularprofile).

FIGS. 37 (a)-(c) show micrographs demonstrating how the microstructureof a fiber can be controlled by the beam intensity profile, and theirresultant tensile test data.

FIGS. 38(a)-(b) shows an example of beam profiles to generate a desiredintensity profile at the laser focus.

FIG. 39 shows an example of a superposition of laser beam spots that aregenerated by a diffractive optic to obtain an approximate intensityprofile at the laser focus that is the sum of all beamlet intensityprofiles generated by the diffractive optic element.

FIG. 40 shows an example of the use of multiple beams to obtain desiredintensity and temperature profiles on the tip and sides of the fiber.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 through 40 illustrate various views and embodiments of thepresent invention, and supporting graphs and data. Various embodimentsmay have one or more of the components outlined below. Componentreference numbers used in the Figures are also provided.

-   10 thermal diffusion region-   15 low molar mass (or LMM) precursor-   20 high molar mass (or HMM) precursor-   25 fiber-   30 concentration gradient-   35 reaction zone-   40 primary heating means-   45 tensioner-   47 tension adjustment device-   50 spooling device/mandrel-   55 coaxial tube-   60 low molar mass (or LMM) precursor tube-   65 high molar mass (or HMM) precursor tube-   70 precursor planar flow sheets-   75 gas bubble-   80 internal thermal diffusion region-   85 external thermal diffusion region-   90 fluid (internal in two phase system)-   95 vessel seals-   100 vessel walls-   101 solid source of HMM precursor (e.g. wax)-   102 liquid source of HMM precursor-   105 nozzle-   110 secondary heating means-   112 return conductor-   115 single partial loop-   120 coils-   125 elongated thermal diffusion region-   130 LLM precursor supply source-   135 wire hot portion-   140 wire manifold-   145 switch connections-   147 control signal-   150 outlet manifold-   155 HMM precursor supply source-   156 feedback means-   160 controller-   165 multi-output analog amplifier-   170 motor controller driver-   200 the vertical axis-   205 the horizontal axis-   210 growth rate data for mixtures of LMM and HMM precursors-   215 curve fit to data-   220 Result #1 (CH₄ at 15 PSI with Xenon)-   225 Result #2 (CH₄ at 30 PSI with Xenon)-   230 Result #3 (CH₄ at 45 PSI with Xenon)-   235 wool-like webbing-   240 baffle-   280 first material-   285 second material-   290 transition portion-   300 mandrel/drum-   310 wiper-   315 fiber bin-   320 substrate-   330 window-   400 smaller diameter sections-   405 larger diameter sections-   410 first composition sections-   415 second composition sections-   420 fiber coating-   425 first coating composition section-   430 second coating composition section-   450 sensing means (or sensors)-   455 translation means-   460 holes/apertures-   465 sensor support surface (or sensing means support surface)-   470 analog/digital and/or multiplexing system-   495 fiber tip-   500 laser beam-   505 focusing lens(es)-   510 focused profiled laser beam-   515 beam intensity profile-   520 induced temperature rise at surface-   525 amorphous carbon-   530 graphitic carbon-   540 beamlets-   545 diffractive optics-   560 first beam-   565 second beam-   570 third beam-   575 aperture-   580 nozzles-   585 focusing reflective or refractive optics-   590 beam splitter

FIG. 1 depicts a thermal diffusion region (sometimes also referred to asa “thermodiffusion region”) 10 surrounding a fiber 25, showing theconcentration gradient 30 that occurs when a mixture of two highlydisparate molar mass precursors are mixed together near the fiber 25.The concentration gradient 30 is not shown in all the figures. The LMMprecursors 15 (usually) tend to concentrate at the region of greatesttemperature, which in this case surrounds the reaction zone (sometimesalso referred to as the growth zone) 35. The HMM precursor 20 species(usually) tend to be displaced away from the reaction zone 35 at theoutside of the thermal diffusion region 10, and as a result, tends tothermally insulate the reaction zone 35. As depicted in FIG. 1, some LMMprecursor 15 may exist outside of the thermal diffusion region 10, andsome HMM precursor 20 may exist in the thermal diffusion region 10. Inaddition, it should be noted that those of skill in the art recognizethat there is often not a well-defined boundary where the thermaldiffusion region 10 ends, but that the concentration gradient 30 maytaper off gradually.

One aspect of some embodiments of this invention is that the reactionzone 35 is thermally insulated by the HMM precursor 20, thereby greatlyreducing heat losses to the surrounding fluids. Much greater growthrates have been observed with vastly reduced input to the power of theprimary heating means 40. Thus, one aspect of the invention's utility isthat it makes the growth of many fibers 25 at once much more efficientand feasible. For example, in the growth of 10,000 fibers at once, whereeach heated spot receives 200 mW of incident power (as is common intraditional laser induced fiber growth), the total energy entering thevessel will be 2 kW. This substantial heat budget must be dealt with orthe temperature in the surrounding gases will rise over time. Thisinvention greatly decreases the power required at each reaction zone 35.Thus, for example, where only 40 mW may be required at each reactionzone 35 with the HMM precursor 20 and LMM precursor 15 mixture, thetotal energy entering the vessel is now only 400 W, which requiressignificantly less external cooling and provides energy savings makingthe process more economically viable.

Note that to prevent excessive homogeneous nucleation, the gases in thethermal diffusion regions 10 may generally be at a lower temperaturethan the threshold for rapid (complete) decomposition of the precursors,but this is not required. Since the thermal diffusion regions 10 andreaction zones 35 overlap close to the growing fiber 25, the thermaldiffusion regions 10 may exceed this temperature. In some cases, it mayeven be useful to induce homogeneous nucleation to provide freshnucleation sites at the fiber 25 tip, and this invention can provide anextended heated region where this can occur.

The reaction takes place inside a reaction vessel, which is anyenclosure that will contain the precursors for the desired life of thesystem and withstand any heat from the primary or secondary heatingmeans(s) 40 or 110. The reaction vessel may be rigid or flexible. Forexample, the reaction vessel could be lithographically-patternedmicrofluidic structures in silicon, a molded polymeric balloon, or amachined stainless steel vessel—there are many possible means toimplement the vessel/enclosure. The reaction vessel may include anynumber of pressure controlling means to control the pressure of thereaction vessel. Non-limiting examples of pressure controlling meansinclude a pump, a variable flow limiter, a piston, a diaphragm, a screw,or external forces on a flexible reaction vessel (that change thereaction vessel internal volume), or through the introduction of solidsthat also effectively change the available internal volume (e.g., theintroduction of HMM precursor 20 in solid form).

As described further herein, the precursors can be introduced in a widevariety of different ways and configurations. As non-limiting examples,the LMM precursor 15 and HMM precursor 20 can be: (1) flowed jointly(pre-mixed) into the reaction vessel; (2) flowed co-axially and directedat a reaction zone(s); (3) flowed in alternating sheets and directed ata reaction zone(s); (4) flowed from alternating sources and directed ata reaction zone(s); (5) flowed from separate sources and directedtangential to the reaction zone; and (6) flowed from separate sourcesand directed at an angle relative to each other.

A wide variety of different LMM precursors 15 and HMM precursors 20 canbe employed in combination in order to obtain the desired thermaldiffusion region and controlling effects. For example, for siliconboride deposition, silane and diborane can be used as LMM precursor 15gases, while HMM precursor 20 gases such as tetraiodosilane, SiI₄, ordecaborane, B₁₀H₁₄, can be used. This list is not intended to beexhaustive, and it is only for explanatory purposes. It is thesubstantive difference in mass and/or diffusivity that is important toachieve the best results. Other examples of LMM precursors 15 and HMMprecursors 20 are outlined in the cross-referenced applications,including U.S. application Ser. No. 62/074,703, incorporated byreference herein.

The HMM precursor 20 species can be introduced as gases, liquids,critical/supercritical fluids, solids, semi-solids, soft plastic solids,glassy solids, or very viscous liquids. Depending on the precursorchosen, the HMM precursor 20 may liquefy, evaporate, or sublime near thereaction zone(s) 35. The HMM precursor 20 species can vary widelydepending on the type of fiber being produced. As non-limiting examples,HMM precursors 20 can be silanes, boranes, organo-aluminum,organo-silicon, organo-boron, metal halide, organometallics,hydrocarbons, fluorocarbons, chlorocarbons, iodocarbons, bromocarbons,or halogenated hydrocarbons species or mixtures thereof. The HMMprecursor 20 may also be inert and not decompose, or have very limiteddecomposition, at the reaction zone 35. The HMM precursor 20 may alsophysically or chemically inhibit the formation of clusters andparticulates near the reaction zone(s) 35.

Similar to the HMM precursors 20, the LMM precursor 15 species can varywidely depending on the type of fiber being produced, and can beintroduced as gases, liquids, critical/supercritical fluids, solids,semi-solids, soft plastic solids, glassy solids, or very viscousliquids. As non-limiting examples, LMM precursors 15 can be silanes,methylsilanes, boranes, organo-aluminum, organo-silicon, organo-boron,metal halide, organometallics, hydrocarbons, fluorocarbons,chlorocarbons, iodocarbons, bromocarbons, or halogenated hydrocarbonspecies or mixtures thereof. Depending on the HMM precursor 20 and theLMM precursor 15, the LMM precursors 15 may (a) react with at least oneHMM precursor 20, causing the LMM precursor to deposit, or partiallydecompose, such that a new “derived precursor species” will be formedand will be concentrated at the reaction zone(s) 35 (and this derivedprecursor decomposing, resulting in the growth of the fiber); or (b) actas a catalyst that decomposes the HMM precursor 20 to a derivedprecursor species (having a lower molar mass than the HMM precursor)that will be concentrated at the reaction zone(s) 35 (and this derivedprecursor species decomposing, resulting in the growth of the fiber).

Depending on the desired fiber characteristics, and HMM precursor 20 andLMM precursors 15 used, the precursors can be in a variety of states.For example: (1) the precursors can all be in a gaseous state; (2) theprecursor(s) concentrated at the reaction zone 35 may be in a gaseousstate while the precursor(s) outside of the reaction zone 35 are in acritical, liquid, or solid state; (3) the precursor(s) concentrated atthe reaction zone 35 may be at the critical point while precursor(s)outside of the reaction zone 35 are in a liquid or solid state; (4) theprecursor(s) concentrated at the reaction zone 35 may be in asupercritical state, while precursor(s) outside of the reaction zone 35are in a supercritical, critical, liquid, or solid state; (5) allprecursors are at the critical point or are in the supercritical fluidstate, or (6) the precursor(s) concentrated at the reaction zone 35 maybe in a liquid state while the precursor(s) outside of the reaction zone35 are in a liquid or solid state. Of course, this is not intended as anexhaustive list. The “liquid” state above can include very viscousliquids or glasses, while the “solid” state can include soft plasticsolids or semisolids. See generally, FIG. 19, which is a table of likelycombinations of different material states.

In some embodiments, an intermediate molar mass (“IMM”) precursor mayalso be introduced into the reaction vessel. Depending on the fiberdesired, and the LMM precursor 15 and HMM precursor 20 used, an IMMprecursor may be introduced to further separate, react with, or breakdown the LMM precursor 15 and/or HMM precursor 20. For example, wherethe HMM precursor is hexadecane (C₁₆H₃₄)[molar mass=226.45 g/mol] andthe LMM precursor is methane (CH₄)[molar mass=16.04 g/mol], an IMMprecursor such as carbon tetrafluoride (CF₄)[molar mass=88.00 g/mol]could be added to react with both the methane and hexadecane, to producea carbon fiber product and hydrogen+hydrogen fluoride by-products. Insome embodiments, the IMM precursor is introduced to primarily reactwith, and break down, the HMM precursor 20 species. For example, wherethe HMM is icosane (C₂OH₄₂)[molar mass=282.56 g/mol] and the LMM issilane (SiH₄)[32.12 g/mol], an IMM precursor such as bromine (Br₂)[molarmass=159.80 g/mol] can be introduced to react with the hydrogen in theicosane to produce carbon as a product (i.e., deposited as part of thefiber) and hydrogen bromide as a byproduct. While the silane,concentrated at the center of the thermal diffusion region will depositspontaneously at low temperatures without bromine being present, thedecomposition of icosane is enhanced through the reaction with bromine.Generally, the molar mass of the IMM precursor is between that of theLMM precursor and HMM precursor.

Just as examples, and not as limitations, the following types of fiberscan be fabricated using the system and methods described herein: boron,boron nitride, boron carbide, carbon, aluminum oxide, aluminum nitride,silicon carbide, silicon nitride, silicon borocarbide, siliconoxynitride, nickel, iron, titanium, titanium carbide, tantalum carbide,hafnium carbide, tungsten, and tungsten carbide fibers, to name just afew. Other examples are outlined in the cross-referenced applications,including U.S. application Ser. No. 62/074,703, incorporated byreference herein.

FIG. 2 depicts one embodiment of the invention; which includes an arrayof thermal diffusion regions 10, reaction zones 35, primary heatingmeans 40, tensioners 45, a tension adjustment device 47, and a spoolingdevice/mandrel 50. The primary heating means 40 is applied to create thereaction zone 35 and thermal diffusion region 10. The spoolingdevice/mandrel 50 rotates to wind the grown fibers 25 onto the spoolingdevice/mandrel 50. Individual spooling devices/mandrels 50 could be usedfor each fiber 25, or many fibers 25 can be wound onto a single spoolingdevice/mandrel 50 to create tow. While shown as an array of growingfibers 25, a similar configuration could be used for growing a singlefiber 25. The optional tensioners 45 can be used to add sufficienttension and alignment to the fibers 25 as they are wound on the spoolingdevice/mandrel 50. Other methods for gathering fibers 25 are known tothose of skill in the art. However, we have developed new methods oftensioning the fiber without holding the end that is growing, whilemaintaining it centered in the reaction zone. We have developedelectrostatic, magnetic, fluidic, and/or mechanical centering/tensioningmeans that can be both passively and actively controlled.

Note that the primary heating means 40 can be any number of optionsknown to those of skill in the art able to create localized reactionzone(s) 35 and thermal diffusion region(s) 10 (either alone or incombination with other primary heating means). As non-limiting examples,primary heating means 40 may be one or more focused spots or lines oflaser light, resistive heating (e.g., passing electrical current throughcontacts on the fiber), inductive heating (e.g. inducing current in thefiber by passing current through coiled wires near or surrounding thefiber), high pressure discharges (e.g. passing current through theprecursors from electrodes to the fibers), focused electron beams,focused ion beams, and focused particle bombardment (e.g. from aparticle accelerator). For reference, radiative primary heating means 40can also use soft X-ray, ultraviolet, visible, infrared, microwave,millimeter-wave, terahertz, or radio frequency radiation (e.g. withinelectromagnetic cavities) to create reaction zones. The primary heatingmeans 40 in FIG. 2 are focused laser beams.

Secondary heating means are not shown explicitly in FIG. 2, but could beused. As described previously, secondary heating means 110 allow furthercontrol and enhancement of the thermal diffusion region 10. This, inturn, allows the real-time modulation and control of the concentrationof LMM precursor 15 species at the reaction zone 35, and hence real-timemodulation and control of fiber geometry and material properties. Asnon-limiting examples, secondary heating means 110 may be energy sourcesfocused into/onto the precursor fluids, such as one or more focusedspots or lines of laser light, focused electron beams, focused ionbeams, or focused particle bombardment (e.g. from a particleaccelerator); secondary heating means may also take the form ofresistive heating of the precursor fluids (e.g., passing electricalcurrent through a wire), inductive heating of the precursor fluids, orhigh pressure discharges through said precursor fluids. Any of thesesecondary heating means 40 can be used individually or in combinationwith one or more other secondary heating means 40.

FIG. 3 depicts one embodiment of the invention where two highlydisparate molar mass precursors are flowed coaxially through a coaxialtube 55, having a LMM precursor tube 60 and a HMM precursor tube 65,directing flow toward the reaction zone 35. In other embodiments, theLMM precursor 15 and HMM precursor 20 can be pre-mixed. Thisimplementation can directly feed the center of the thermal diffusionregion 10, increasing the growth rate of the fiber 25 by reducing theprecursors' transport time through the fluid. Again, the LMM precursor15 usually tends to concentrate at the region of greatest temperaturesurrounding the reaction zone 35. The HMM precursor 20 species tends tobe displaced away from the reaction zone 35 at the outside of thethermal diffusion region 10, and as a result, tends to thermallyinsulate the reaction zone 35. Thus, the LMM precursor 15 is decomposedin the reaction zone 35 and deposits, resulting in fiber growth.

Thus, in one embodiment of the invention that uses the methods of FIGS.2 and 3 to fabricate fibers, at least one LMM precursor 15 is flowedinto a reaction vessel and at least one HMM precursor 20 is introducedto the reaction vessel. As described above, the HMM precursor 20preferably has a molar mass 1.5 to 3 times greater, and more preferably3 or more times greater, than the LMM precursor 15, and preferably athermal conductivity substantively lower than that of the LMM precursor15. One or more reaction zone(s) 35 are created within the reactionvessel by one or more primary heating means 40, resulting in thedecomposition of at least one precursor species. The decompositionresults in the growth of a solid fiber(s) 25 at each reaction zone(s)35. The solid fibers 25 have a first end at or near the reaction zone(s)35 and a second end that is drawn backward through a tensioner 45 andspooling device/mandrel 50 at a rate to maintain the first end withinthe reaction zone(s) 35. One or more thermal diffusion region(s) 10 areestablished at/near said reaction zone(s) 35 to partially or whollyseparate said LMM precursor 15 species from said HMM precursor 20species using the thermal diffusion effect, thereby concentrating theLMM precursor 15 species at each reaction zone(s) 35. In thisembodiment, the concentrated LLM precursor 15 substantively enhances thegrowth of the solid fiber(s) 25 and the HMM precursor 20 speciesdecreases the flow of heat from the reaction zone(s) 35, relative tothat which would occur using the LMM precursor 15 species alone.

FIG. 4 shows another embodiment of the invention, where two highlydisparate molar mass precursors are flowed in precursor planar flowsheets 70 toward the reaction zones 35 of an array of fiber(s) 25. Thisimplementation can also directly feed the center of the thermaldiffusion regions 10 in the array, increasing the growth rate of thefiber(s) 25 by reducing the precursor's transport time through thefluid. The fibers 25 are drawn backward (as shown by the arrows) as thereaction zones 35 and thermal diffusion regions 10 remain substantiallystationary in space. For practical considerations, this arrangement ofstationary reaction zones and thermal diffusion regions is oftenpreferred, but not required. Again, the LMM precursor 15 usually tendsto concentrate at the regions of greatest temperature surrounding thereaction zones 35. The HMM precursor 20 species tends to be displacedaway from the reaction zone 35 at the outside of the thermal diffusionregions 10, and as a result, tends to thermally insulate the array ofreaction zones 35. Again, the LMM precursor 15 is decomposed in thereaction zone 35 and deposits, resulting in fiber growth.

As shown in FIG. 4, the planar sheets 70 may alternate between LMMprecursor 15 and HMM precursor 20, where the LMM precursor 15 flowsdirectly into the thermal diffusion region 10. Any number of fibers 25can be grown in this configuration. And any of the alternate primaryheating means discussed above can be used, but are not shown in FIGS. 3and 4.

Thus, from FIGS. 3 and 4, one can see that precursors can be introducedin a wide variety of different ways and configurations, including butnot limited to (1) flowed jointly (pre-mixed) into the reaction vessel;(2) flowed co-axially and directed at a reaction zone(s) 35; (3) flowedin alternating sheets and directed at a reaction zone(s) 35; (4) flowedfrom alternating sources and directed at a reaction zone(s) 35; (5)flowed from separate sources and directed tangential to the reactionzone 35; and (6) flowed from separate sources and directed at an anglerelative to each other. IMM precursors may also be used, and introducedas described above. As discussed above, depending on the desired fibercharacteristics, a wide variety of HMM precursors and LMM precursors incan be used. The reaction vessel may also optionally include thepressure controlling means discussed above.

It is important to note that the thermal diffusion region 10 need notonly be in the gas phase, but may also occur within liquid precursors,critical or supercritical fluids, or combinations of the same. Thus, amixture of LMM precursor 15 and HMM precursors 20 can enter the reactionvessel as a liquid and remain so within the thermal diffusion region 10within the liquid. However, in another implementation, the liquidmixture of HMM precursors 20 and LMM precursors 15 can transform locallyinto a gas at each reaction zone 35, thereby producing a thermaldiffusion region 10 within a gas bubble, and a secondary thermaldiffusion region 10 in the liquid. Alternatively, one or moreprecursors, often the HMM precursors 20, can be driven into the reactionvessel as viscous liquids (e.g. silicone oils), viscoelastic polymers(e.g. pitch, rosin), and plastic solids (such as waxes or pitch), which,upon heating, will evaporate and surround each reaction zone 35, therebycreating a thermal diffusion region 10 at each reaction zone 35. In thiscase, the LMM precursors 15 can be provided as part of the solid orviscous liquid, or they can be flowed into the reaction vesselseparately.

For example, FIG. 5 shows another embodiment of the invention havingthermal diffusion regions that exist in a two-phase, gas+liquid system.In this embodiment, a gas bubble 75 is created. Within the gas bubble75, there is an internal thermal diffusion region 80 and a reaction zone35. Also, within the liquid there will be a second, external thermaldiffusion region 85. Separation between the HMM and LMM precursors canoccur in both regions 80, 85, and the properties of the precursors(including mass) determine the degree of separation in each. Again, thefiber(s) 25 are drawn backwards (shown by the arrow) in this embodiment,while the gas bubbles 75, the thermal diffusion regions 80, 85, and thereaction zones 35 remain substantially stationary in space.

FIG. 6 shows another embodiment of the invention having two thermaldiffusion regions 10 that exist in a “two-phase” system, where one fluid90 (e.g. a critical/supercritical fluid), can be present around thereaction zone 35, and an internal thermal diffusion region 80 can existwithin this fluid 90. Outside of the internal thermal diffusion region80, another external thermal diffusion region 85 can exist withinanother fluid or solid phase. Separation can occur in both regions 80,85, and the properties of the precursors (including mass) determine thedegree of separation in each. This embodiment may be utilized, forexample, when a highly pressurized liquid or solid precursor mix isheated by one or more primary heating means 40.

FIG. 7(a) shows one embodiment of the invention where a solid source(wax in FIG. 7(a)) of HMM precursor 20 is evaporated by one or moreprimary heating means 40 or secondary heating means 110 (not shown) neara gaseous thermal diffusion region 10. This solid source can beintroduced at or near the thermal diffusion region 10 in numerous waysincluding extrusion through vacuum/pressure seals 95 in the vessel walls100. Again, the reaction zone 35 and thermal diffusion region 10 remainstationary in this embodiment, while the fiber 25 is drawn backwards (asshown by the arrow). The LMM precursor 15 can be flowed separatelythrough a nozzle 105 to the reaction zone 35, and can be placed inmultiple possible orientations, including through a tube in the solidsource of HMM precursor 20 (not shown). It is also possible to entrapthe LMM precursor 15 within the HMM precursor 20 solid, and to releaseboth at the thermal diffusion region 10.

FIG. 7(b) shows another embodiment of the invention using a liquidsource of HMM precursor 102. The liquid source can be stationary orflowing below the thermal diffusion region 10, where the liquidevaporates to provide the HMM precursor 20. Also shown is a LMMprecursor tube 60 for introducing the LMM precursor 15. It is alsopossible to dissolve or entrap the LMM precursor 15 within the HMMprecursor 20 liquid, and to release both at the thermal diffusion region10.

In the embodiments shown in FIGS. 7(a) and (b), the primary heatingmeans 40 is depicted as a focused laser beam. As discussed herein, otherprimary heating means 40 can be used, and secondary heating means 110(not shown) can be employed to control the thermal diffusion region.

FIG. 8(a) shows another embodiment of the invention using a secondaryheating means 110 (a resistive wire) to heat the thermal diffusionregion 10 at the reaction zone 35 of the fiber 25. In this embodiment,the secondary heating means 110 in the thermal diffusion region 10 is aresistive wire preferably of fine diameter, and of resistance sufficientto provide a desired heating rate for the voltage applied. Outside ofthis region, it could be of larger diameter and/or conductivity toreduce heating elsewhere. In one embodiment, shown in FIG. 8(a), thesecondary heating means 110 (wire) has a single partial loop 115. Thesecondary heating means 110 and single partial loop 115 use resistiveheating to heat the fiber and surrounding gas to create and/or enhance athermal diffusion region 10 and reaction zone 35 around the tip of thefiber 25. FIG. 8(a) also shows the use of a primary heating means 40,which in this embodiment, is a focused laser beam.

FIG. 8(b) shows another embodiment of the invention using a secondaryheating means 110 comprised of a wire coil 120 surrounding a fiber 25.This allows the creation of an elongated thermal diffusion region 125.This wire coil 120 could also be considered a primary heating means, ifit were to raise the temperature of the fiber and reaction zone throughinductive heating.

Thus, in many embodiments (as shown in FIG. 8(a) and (b)), both primaryand secondary heating means 40 and 110 are commonly used. In general, wedistinguish a primary heating means 40 as the primary driving force thatinduces decomposition of the precursor at a reaction zone 35; while asecondary heating means generally drives/controls the fluid temperatureand thermal diffusion region 10 surrounding a fiber 25. In practice, aprimary heating means 40 can also influence the temperature of the fluidand the thermal diffusion region 10 through heat conduction to the fluidfrom the fiber, and a secondary heating means 110 can influence thetemperature of the fiber 25 (and reaction zone 35) through heatconduction to the fiber from the gas. However, in most implementations,the temperature at the reaction zone is higher than that of thesurrounding fluids, and heat tends to flow from the fiber to itssurroundings, which allows the primary heating means (incident on thefiber) to dominate the local temperature of the reaction zone 35, andthe secondary heating means to dominate control of the size, shape, andgradient of the thermal diffusion region 10 (which extends outward fromthe fiber). Careful design and placement of the secondary heating meanscan enhance this control.

As mentioned before, when a secondary heating means is used, in additionto influencing the thermal diffusion region, it can partially decomposethe HMM precursor 20 or LMM precursor 15 near the reaction zone 35,thereby creating another set of precursor species of even lower molarmass (which we denote as a “derived precursor species”).

Thus, in one embodiment of the invention for fabricating fibers, atleast one LMM precursor 15 is flowed into a reaction vessel and at leastone HMM precursor 20 is introduced to the reaction vessel. As describedabove, the HMM precursor 20 preferably has a molar mass 1.5 to 3 timesgreater, and more preferably three or more times greater than the LMMprecursor 15, and preferably a thermal conductivity substantively lowerthan that of the LMM precursor 15. One or more reaction zone(s) 35 arecreated within the reaction vessel by one or more primary heating means40, resulting in the decomposition of at least one precursor species.The decomposition results in the growth of a solid fiber(s) 25 at eachsaid reaction zone(s) 35. The solid fibers 25 can have a first end at ornear the reaction zone(s) 35 and a second end that is drawn backwardthrough a tensioner 45 and wound on a spooling device/mandrel 50 at arate to maintain the first end within the reaction zone(s) 35. Othermeans can be used to remove the fiber from the reaction zone. One ormore thermal diffusion region(s) 10 are established at/near saidreaction zone(s) 35 to partially- or wholly-separate said LMM precursor15 species from said HMM precursor 20 species using the thermaldiffusion effect, thereby concentrating the LMM precursor 15 species ateach reaction zone(s) 35. In this embodiment, a secondary heating means110 using a heated wire is passed through or configured in proximity tothe reaction zone 35 to further concentrate the LMM precursor 15 speciesat/near said heated wire(s) and reaction zone(s) 35, and theconcentrated LLM precursor 15 substantively enhances the growth of thesolid fiber(s) and the HMM precursor 20 species decreases the flow ofheat from the reaction zone(s) 35, relative to that which would occurusing the LMM precursor 15 species alone. Although one wire is shown inFIGS. 8(a) and (b), multiple wires can be used. Also, the wire canencircle the reaction zone 35. The term “encircle” is used to describethat the wire surrounds the reaction zone, but not necessarily in acircular configuration. For example, the wire can “encircle” thereaction zone in a star configuration, square configuration, circleconfiguration, or other desired shape. In this implementation, IMMprecursors may also be used. As discussed above, depending on thedesired fiber characteristics, a wide variety of HMM precursors 20 andLMM precursors 15, in various forms (gas, liquid, solid, critical,supercritical, etc.) can be used. The reaction vessel may alsooptionally include the pressure controlling means discussed above. Insome related embodiments, each reaction zone 35 has only one primaryheating means 40, while in other embodiments, each reaction zone has twoor more primary heating means 40.

FIG. 9(a) shows another embodiment of the invention used to fabricatesolid fiber(s). Generally, at least one LMM precursor 15 species isintroduced, or flowed into a vessel, in proximity to at least onesecondary heating means 110 (e.g. the heated wire shown), and at leastone HMM precursor 20 species is introduced into the vessel. As discussedabove, the HMM precursor 20 preferably has a mass substantively greaterthan the LMM precursor 15 species, and preferably of thermalconductivity substantively lower than that of the LMM precursor 15species. The HMM precursor 20 can be provided by any of the othermethods discussed herein. In this implementation, the thinner, hotportion of the wire 135, creates an elongated thermal diffusion region10; this elongated thermal diffusion region geometry provides apreferred conduit that follows the secondary heating means 110 (wire inthis embodiment), along which the LMM precursor 15 will flow to reachreaction zones 35. The array of reaction zones 35 are created within thevessel by one or more primary heating means 40 (not shown for clarity),and decomposition of at least one of the precursor species occurs; thisdecomposition results in the growth of solid fiber(s) 25 at each saidreaction zone(s) 35. The solid fibers 25 have a first end at thereaction zone(s) 35 and a second end that is drawn backward (shown bythe arrow). The second end can be drawn backward by a spoolingdevice/mandrel 50 (not shown) and may include a tensioner 45 (notshown). Preferably, the second end(s) are drawn at a rate to maintainthe first end(s) within the reaction zone(s) 35.

In a related implementation to FIG. 9(a), at least one thermal diffusionregion 10 is created or established at/near the reaction zone(s) topartially or wholly separate the LMM precursor 15 species from the HMMprecursor 20 species using the thermal diffusion effect, therebyconcentrating the LMM precursor 15 species at each reaction zone(s) 35.A secondary heating means 110 (wire in this embodiment) is passed orconfigured in proximity to the reaction zone(s) 35, to furtherconcentrate the flow of LMM precursor 15 species along the heatedwire(s) and into the reaction zone(s) 35 using the thermal diffusioneffect, thereby creating a selective conduit to flow the LMM precursor15 species to the reaction zone(s) 35. By concentrating the LMMprecursor 15 species as described, it substantively enhances the growthof solid fiber(s) 25, and the HMM precursor 20 species substantivelydecreases the flow of heat from said reaction zone(s) 35, relative tothat which would occur using the LMM precursor 15 species alone.

FIG. 9(b) shows another embodiment and implementation, where one or moresources of LMM precursor 130 supply LLM precursor 15 to a manifold ofthermal diffusion conduits 140, where the LLM precursor 15 branches andflows along individual thermal diffusion conduits, created by individualsecondary heating means 110 (wires) that can be electrically-modulatedvia switches (represented by the transistor symbol). As the electricalcurrent can be switched away from the reaction zones 35 to thetransistors, the switch connections 145 acts as “thermal diffusivevalves” that modulate the instantaneous flow of the LLM precursor 15 to(or away from) each fiber 25. In FIG. 9(b), the HMM precursor 20 isprovided by a HMM precursor supply source 155, but the HMM precursor 20can be provided by any of the other methods discussed herein. Inaddition, the byproducts of the reaction are also carried along thesecondary heating means 110 (wire), and given the general flowdirection, tend to be removed at separate outlet manifolds 150. In thisway, the thermal diffusion regions 10 and secondary heating means 110“conduits” can be used to remove byproducts that can otherwise affectthe reaction. Thus, in some embodiments, byproduct species from thedecomposition are flowed away from the reaction zone 35 along one ormore of the secondary heating means 110, thereby removing the byproductspecies from the reaction zone 35, and dispersing them into the reactionvessel, or allowing them to be removed from the reaction vesselaltogether (for example, via an outlet manifold 150). Separate inletsare provided for the MINI precursor supply source 155, as shown.

Also remember that using the embodiment of FIG. 9(b), the electricalcurrent in the wire can be controlled to modulate the concentration ofLMM precursor 15 and HMM precursor 20 present at the reaction zone 35,thereby controlling the decomposition and growth of the solid fiber 25independent of the primary heating means 40 (not shown for clarity). Bymodulating the concentration of the precursors, solid fibers can begrown with desired geometries, diameters, microstructures, compositions,physical properties, chemical properties, coatings (including presence,absence, or thickness of the coating), and growth rates (collectivelyreferred to herein as “fiber characteristics”).

In a similar embodiment to the invention of FIG. 9(a), each secondaryheating means 110 (wire) may be comprised of two or more thin wiresections, with a thicker (less resistive) short section in-between. Thisin-between section may be heated by a laser beam (or other heatingmeans) to modulate the flow of the LMM precursor 15 to the reaction zone35, effectively creating a structure similar to a “thermal diffusiontransistor.” In another implementation, one or more sections may haveattached cooling fins that may be heated resistively and used tomodulate the flow of the LMM precursor 15 to the reaction zone 35(another form of a thermal diffusion switch/transistor). In anotherimplementation, one or more of the secondary heating means 110 (wire)sections may also have attached dispersion wires that may be heatedresistively to disperse the LMM precursor 15 species elsewhere and usedto modulate the flow of LMM precursor 15 species in real-time to thereaction zone(s) 35 (i.e., the dispersion wires act as an inversethermal diffusion valve). The heated wires may also be in the form of amicrotube that is heated by passing hot fluid through the microtube.

In most embodiments, the invention incorporates feedback means tomeasure characteristics of the fibers 25 being fabricated, and then usethis feedback to control one or more aspects of the fabrication processand ultimately fiber characteristics/properties. Measurements of thegeometry, microstructure, composition, and physical properties of thefibers can be made as they are grown. This feedback can be used tocontrol the primary heating means(s) 40 and/or secondary heating means110. For example, in FIG. 9(b), the electrical current through thesecondary heating means 110 (which form the conduits of manifold 140)can be controlled to alter the ongoing fabrication of the fibers 25.This can be done independently, or at least partially independently, ofany primary heating means 40 being used. For example, if the feedbackmeans detects a composition of a fiber that results from aless-than-optimum LMM precursor concentration at the reaction zone 35,the current through the wire can be increased, thereby increasing thetemperature of the wire, and flowing additional LMM precursor throughthe conduit to obtain the desired fiber composition.

The feedback means (not shown in FIG. 9(b) include electromagneticsensing devices and can be of various types known to those of skill inthe art. A non-exhaustive list of examples of feedback means includereal-time FT IR spectroscopy, Raman spectroscopy, fluorescencespectroscopy, X-ray analysis, two and three color pyrometrymeasurements, and optical, UV, and IR imaging, narrow band detection ofemission/absorption lines, reflectivity/absorption measurements, etc.Similarly, feedback means for the concentration/density of LMMprecursors 15 and HMM precursors 20 species in the thermal diffusionregions 10 and/or reaction zones 35 can be obtained using real-timeshadowgraphy, Schlieren techniques, and spectroscopy techniques. Inother embodiments, the feedback means can be acoustic sensing devices.This is not intended as an exhaustive list. Various feedback means canbe used individually or in combination.

Other devices and methodologies can also be used to obtain feedback ofthe process, and control the fabrication. In some embodiments, eithertogether with one or more of the options discussed above, or by itself,the thermal diffusion regions 10 and/or the reaction zone 35 can bemeasured with real-time shadowgraphy or Schlieren imaging techniques toobtain feedback on the relative concentration/densities of the LMMprecursors 15 species relative to the HMM precursor 20 species. Thus, inthis embodiment, the feedback means is measuring the thermal diffusionregion 10 and/or the reaction zone 35, rather than the fibercharacteristics. This feedback can be used as input to control one ormore aspects of the fabrication process, for example, modifying theprimary heating means 40 or secondary heating means 110 to obtain solidfibers at a desired rate with desired fiber characteristics.

FIG. 10 shows another embodiment of the invention. In this embodiment, aseries of secondary heating means 110 (in the form of wires) areconnected to a current source (not shown) and converge on and surroundthe reaction zone 35 of fiber 25. The flow of current through anyparticular wire 110 can be regulated to control the heating rate of thatwire. In one embodiment where the LMM precursor 15 and HMM precursor 20are in a gas mixture, the concentration of the LMM precursor 15 can bevaried by modulating the amount of current in the wires 110. When allthe wires 110 are heated, the LMM precursor 15 is drawn out of thesurrounding gas mixture and is concentrated at the reaction zone 35.When the wires are turned off, the concentration of LMM precursor 15 isdiminished. The primary heating means 40 in this embodiment is a focusedlaser beam. The return conductor 112, provides a return path for thecurrent from wires 110.

FIG. 11 shows a flow diagram of one embodiment of the invention withfeedback means 156 which are used to control the growth of multiplefibers, by modulating the reaction zones 35 (shown) and thermaldiffusion regions 10 (not shown). In this particular implementation, avision system is used as the feedback means 156, which can track thegrowth and characteristics of many fibers at once. Based on the inputfrom the vision system, a controller 160 determines what parameterchanges in the fabrication process need to be made, if any, to achievethe desired fiber growth rates and properties; the controller 160contains the necessary hardware and software to receive the visionsystem inputs and pass appropriate signals to a multi-output analogamplifier 165 and/or motor controller driver 170. Here, the analogamplifier 165 provides current to the secondary heating means 110 (whichare in the form of wires). The current in the wires control the thermaldiffusion region (not shown) and concentration of LMM precursor inreaction zones 35. The return path for the current in each wire is notshown. With input from controller 160, the motor controller driver 170controls the spooling device/mandrel 50, and the winding rate of thefiber. In this way, controller 160 can modulate/control the fiber growthrate and properties, such as diameter, composition, microstructure, andbulk material properties—as well as process parameters such as precursorconcentrations, flow rates, pressures, and induced temperatures. Thecontroller 160 and its various configurations and interactions with theother elements used to control fiber growth and properties may bereferred to herein as “controlling means.”

Thus, in one embodiment, the invention comprises a system forfabricating solid fiber(s) 25 having one or more reaction vessels, eachreaction vessel containing or having an associated one or more primaryheating means 40 and one or more secondary heating means 110. In use,the primary and secondary heating means create one or more reactionzones 35 and thermal diffusion regions 10 in each reaction vessel wherefibers 25 are grown. The system can incorporate one or more spoolingdevices/mandrel 50 and tensioners 45 for grown fibers 25. The system canalso include one or more precursor inlet channel(s), and one or morebyproduct outlet channels. In practice, a precursor inlet channel allowsthe flow of LMM precursor 15 and HMM precursor 20 to flow into thereaction vessel. The primary heating means 40 can remain activated andcan provide a relatively steady temperature in the reaction zone 35 andthermal diffusion region 10. The secondary heating means 110 can then beused to modulate/control the concentration of the LMM precursor 15relative to the HMM precursor 20 at the thermal diffusion region(s) 10and reaction zones 35. As before, any of the heating means discussedherein can be used for the primary heating means 40 and for thesecondary heating means 110.

In one embodiment, the secondary heating means 110 is chosen from thegroup of: resistively heated wire(s), or focused infrared-, microwave-,millimeter-wave-, terahertz-, or radio-frequency electromagneticradiation. If a resistively heated wire is used, in some embodiments,the heated wire(s) passes through, or encircles, the reaction zone(s)35. In other embodiments, heated wires are interconnected to create atleast one thermal diffusive valve. In some embodiments, the heated wireextends to the precursor inlet channel, creating a thermal diffusiveconduit to the reaction zone 35 and thermal diffusion region 10, and/orthe heated wire extends to the byproduct outlet channel thereby creatinga thermal diffusive conduit (for example, see FIG. 9(b)). The samefeedback means and control devices discussed above can be used tocontrol the process (for example, the secondary heating means) tocontrol the fiber characteristics of the fibers 25 being fabricated.

FIG. 12 is a graph showing the growth rate chart of a particularembodiment of the invention using methane as the LMM precursor 15 andvarious more massive hydrocarbon HMM precursors 20, at different LMM:HMMpartial pressures. The vertical axis 200 represents the growth rate ofthe fiber relative to the expected growth rate of pure methane at thesame methane partial pressure. The horizontal axis 205 represents theratio of methane to the hydrocarbon HMM precursor partial pressures. Thedata 210 shows that when the partial pressure of the HMMP precursor islarge enough (i.e. >¼^(th) that of the methane), a growth enhancement ofat least one order of magnitude occurs relative to that of pure methane.The line 215 is curve fit to this data, and approaches the growth rateof pure methane as the HMMP partial pressure approaches zero.

FIG. 13 is a graph showing the growth rate chart of a particularembodiment of the invention using methane as the LMM precursor 15 andXenon as the HMM precursor 20, at different pressures. Result #1 220shows the graph for CH₄ at 15 PSI, Result #2 225 shows the graph for CH₄at 30 PSI, and Result #3 230 shows the graph for CH₄ at 45 PSI. Thevertical axis shows the growth rate of the fiber 25 in μm/s and thehorizontal axis shows the Xenon pressure in PSI. This result also showsa large enhancement in the growth rate of methane, simply by adding aninert HMM precursor that is much more massive than the LMM precursor.

FIG. 14 shows expected thermal diffusion region separation graphs forgases. These graphs provide a (normalized) measure of the expectedseparation during fiber growth, given gaseous precursors of differentmasses (one LMM precursor 15, one HMM precursor 20), with a constantflow velocity. Two thermal diffusion region 10 geometries are provided(cylindrical and spherical) with various sized thermal diffusion regions10 (which depend on pressure and the induced temperature by the primaryheating source 40 as well as the secondary heating source(s) (e.g. wires110)). Changing the size of the thermal diffusion region 10 directlyaffects the concentration of LMM and HMM precursors near/at the reactionzone 35, which will in turn affect the growth rate of the fiber(s) 25.

FIG. 15 shows expected thermal diffusion region separation graphs forliquids. These graphs provide a (normalized) measure of the expectedseparation during fiber growth, given liquid precursors of differentmasses (one LMM precursor 15, one HMM precursor 20), with a constantflow velocity. Two thermal diffusion region 10 geometries are provided(cylindrical and spherical) with various sized thermal diffusion regions10 (which depend on pressure and the induced temperature by the primaryheating means 40 as well as the secondary heating means (e.g. wires110)). Changing the size of the thermal diffusion region 10 directlyaffects the concentration of LMM and HMM precursors near/at the reactionzone 35, which will in turn affect the growth rate of the fiber(s) 25.

FIG. 16 shows one embodiment of this invention using a baffle. In thisembodiment, the thermal diffusion region 10 can be protected by awool-like webbing 235 and/or baffle 240 that prevents advection fromovercoming the thermal diffusion region 10. The baffle 240 may be asolid structure, or can be a solid structure with holes or perforations.In the embodiments using a wool-like webbing 235 with a baffle 240“conduit,” the wool-like webbing 235 can be on the outside or the insideof the baffle 240 “conduit”. A means for cooling the gas in the outerregion of the thermal diffusion region 10, or outside of the thermaldiffusion region 10, can also be used, including use of a heat sink,heat pipe, or actively cooled porous surface place near/at the boundaryof a thermal diffusion region 10. FIG. 16 shows a cooling fluid flowthrough a channel in the baffle 240 for cooling.

FIG. 17 is a graph a graph showing the axial growth rate of carbonfibers using pure methane as the precursor, at different pressures.

FIG. 18 is a graph depicting thermal diffusion region separations bymass difference. This provides a (normalized) measure of the separationthat would be expected during fiber growth, given a spherical geometry,with all precursors as gases in the thermal diffusion region, and withconstant flow. This model assumes all precursors are ideal gases andthat the thermal diffusion constant (alpha) is independent oftemperature, intermolecular forces, etc. Note that very largeseparations can occur as the ratio of the HMM mass to LMM massesincreases.

FIG. 19 depicts a table of likely combinations of different materialstates that may be used in various embodiments of the invention. Thisdoes not consider those combinations that are practically impossible toimplement due to the usual shape of the P-T phase diagram for mostmaterials.

While the disclosure above primarily discusses decomposition anddisassociation of the precursors using various heating means, it shouldbe recognized that other methods can also be used. For example, theprecursors can be decomposed chemically, using x-rays, gamma rays,neutron beams, or other systems and methodologies. Additionally, whilemany embodiments discuss drawing the fiber backward during fabrication,and largely keeping the reaction zone stationary, it should berecognized that the fiber could remain stationary, and the reaction zone35 and/or thermal diffusion region 10 moved. For example, the placementof the primary heating means(s) 40 can be moved. In one embodiment usinga stationary fiber, if a laser beam is used as a primary heating means40, the direction/orientation of the laser beam can be changed, thelaser can be placed on a moveable, translatable mount, or various opticsand lenses can be used to alter the focus of the laser. Similarly, ifheated wires are used as the primary heating means 40, the wires can bemoveable and translatable such that the thermal diffusion region 10and/or reaction zone 35 can be moved.

Additionally, while the disclosure primarily relates to and utilizes LMMprecursors and HMM precursors having highly disparate molar masses, themodulation of the thermal diffusion region 10 and/or reaction zone 35,can still be utilized, and highly beneficial, for many different typesof precursors, even when their respective molar masses are notsubstantively different.

Recording Information on Modulated Fibers, Microstructures, and Textilesand Device for Reading the Same

As further described herein in some embodiments, methods and systems aredisclosed for recording and reading information stored on or withinmodulated fibers, microstructures, and textiles. It should be noted thatwhile the HMM precursor species and LMM precursor species discussedabove can be used as precursors for recording information on modulatedfibers as discussed below, depending on the desired characteristics ofthe fibers, the precursors need not share the same characteristicsdiscussed above with respect to the difference between the HMM precursorand LMM precursor. Indeed, some embodiments of the systems and methodsfor recording information on fibers and microstructures do not requireuse or manipulation of a thermal diffusion region. Any number of systemsand methods can be used to decompose and grow fibers, including highpressure laser chemical vapor deposition and chemical vapor deposition,hyperbaric laser chemical vapor deposition, electron beam deposition,ion beams, photolysis, and various focused energy sources. Recording andreading information in a fiber-based format is novel in itself.

FIG. 20 depicts different means of encoding information in or on fibers25. In one implementation, data can be represented as discrete or analogchanges in a surface coating on a fiber (FIG. 20(a)). For instance, a“0” can be represented by a first coating composition section 425, and a“1” by a second coating composition section 430. In one embodiment, onlyone coating composition is used on only portions of the fiber; data canbe encoded through the presence/absence of a surface coating or throughthe variable properties of a surface coating on the fibers—which wascreated during or subsequent to the growth of fibers. For example, thedifference in activation energies between two precursors can cause themto selectively grow in a fiber. But, depending on the radialdistribution of the primary heating means (relative to the axis of thefiber), one material can grow at the core of the fiber, while the otheris concentrated as a coating on the outside of the core. Through carefulmanipulation of the radial distribution of heating, the coating can bemade to appear and to disappear. This can also be accomplished throughthe use of another heating means (for example, behind the first), sothat the core grows only one material, but the second material is added(or not) as a coating over the first.

In another embodiment of the coating method of FIG. 20(a), two or morecoating composition sections can be utilized. These can be grown fromdifferent precursors over existing fibers, or from multi-precursormixtures, where two coating compositions are alternately preferred onthe surface of the fiber as the primary (or secondary) heating means arevaried. In another embodiment the precursors are supplied in nozzles andalternated rapidly to induce alternating coatings.

Importantly, in all of these methods of FIG. 20, the lengths of thecoating composition sections can also vary, which can also representdigital or analog values. Also note that although the primaryembodiments shown in the figures are encoded as digital patterns, theinformation could also be encoded in analog compositional gradients orgeometric gradients (e.g. coating composition changing slowly along thelength). In addition more than two materials or geometries can be usedto encode information.

In another implementation, shown in in FIG. 20(b), the composition ofthe fiber itself can be varied in discrete or blended (analog) ways. Forinstance, a “0” can be represented by a first composition section 410,and a “1” can be represented by a second composition section 415. Aspecific example would be a first composition section 410 comprised ofsilicon and a second composition section 415 comprised of siliconcarbide. Many other materials could be used; this example is forexplanatory purposes only. In addition, more than two types ofcomposition sections can be utilized, and the lengths of the compositionsections can vary.

One means of encoding alternating materials vs. length is where twoprecursors are used to grow fibers simultaneously (as disclosed inabove, and in provisional U.S. application Ser. No. 62/074,703, entitled“Doped Carbon Fibers and Carbon-Alloy Fibers and Method of FabricatingThereof from Disparate-Molecular Mass Gaseous, Liquid, and SupercriticalFluid Mixtures”, filed on Nov. 4, 2014, and incorporated by referenceherein), and these decompose at different temperatures (e.g. through adifference in rate constants or activation energies), a change intemperature can select for one material over another. For example, asilicon precursor, such as disilane (Si2H6), can be used to grow siliconfibers, but a carbon precursor, e.g. benzene, can be used to providesilicon carbide deposits. Disilane begins to decompose appreciably at690-920 K, while benzene decomposes between 950-1200 K. Varying thereaction zone temperature during growth gives differing amounts ofcarbon in the deposit versus length. And since the length scale of thereaction zone is small, this temperature can be changed rapidly (on theorder of femtoseconds to milliseconds). For example, in some embodimentsusing a laser as a primary heating means, the timing of the laser beam(or the power of the laser beam) can be controlled to change thetemperature. In a similar implementation, a single precursor that bearstwo or more elements can be used to deposit one element at onetemperature and another element at a higher temperature. For example,the precursor ferrocene, Fe(C5H5)2, is comprised of an iron atom withtwo attached cyclopentadienyl ligands (C5H5). At a low temperature, theiron is separated from the C5H5 ligands and is deposited withoutdecomposition of C5H5 ligands themselves. At a higher temperature,however, the C5H5 ligands will also decompose, adding carbon to the irondeposits. In another implementation, two precursors with widelydifferent masses or diffusive properties can be used to select onematerial over another by having a high concentration of the desiredmaterial at the reaction zone during writing (e.g., fiber creation) andexcluding the other. For instance, since disilane has a molecular massof 78 amu, and methane has a molecular mass of 16 amu, one could usetheir differing thermal diffusivities to select for methane at thereaction zone through the thermal diffusion effect. These samecharacteristics of different reactions at different temperatures,differing masses, and differing thermal diffusivities exist with thedifferent precursors disclosed above, and provisional U.S. applicationSer. No. 62/074,703, entitled “Doped Carbon Fibers and Carbon-AlloyFibers and Method of Fabricating Thereof from Disparate-Molecular MassGaseous, Liquid, and Supercritical Fluid Mixtures”, filed on Nov. 4,2014, and can be used herein depending on the specific characteristicsdesired.

The composition-variation approach (FIGS. 20(a) and (b)) can lead tomultiple means of encoding and reading information, through the changingproperties of the material. For instance, the change in compositioncould lead to bits/bytes encoded as specific electrical conductivities,dielectric constants, thermal conductivity/capacity, opticaltransmittance, reflectance, and/or absorbance, or selective chemicalreactivity/bonding, dangling bonds, or wetting characteristics at thesurface of the fibers. It could also be implemented to add small dopantsinto semiconducting fibers, where small additions of dopants lead tovery large changes in local electrical conductivities. These variousmaterial properties would obviously need to be read in different ways,including: optically, capacitively, resistively, inductively,chemically, mechanically, etc. And more than one read-out method can beused to improve the read accuracy. The changes in composition need onlybe sufficient to cause detectable differences in the desiredcharacteristic. For example, if electrical conductivity is thecharacteristic to be read, the materials deposited as part of the fiberpreferably have sufficiently different electrical conductivities toallow for detection. The same is true for the other propertycharacteristics, e.g., dielectric constants, thermalconductivity/capacity, optical transmittance, reflectance, and/orabsorbance, or selective chemical reactivity/bonding, dangling bonds, orwetting characteristics at the surface of the fibers.

It is also possible during use of one or more precursors to induce achange in the microstructure of a fiber locally, e.g. to create moresp3-bonded carbon versus sp2-bonded carbon that can be read in variousmeans, e.g. optically by their relative Raman peaks. Graphite(reflective) and glassy carbon (absorptive) also possess differentoptical properties that can be read optically. There are many differentmeans through which changes in microstructure can be used to encodeinformation.

As shown in FIG. 20(c), the fiber 25 geometry can also be utilized toencode discrete or analog information, for example by creating varyingfiber diameters along its length; for example, smaller diameter sections400 can represent “0,” and larger diameter sections 405 can represent“1.” Alternatively, different geometry configurations can be used, forexample using a circular cross-section in one section, and a squarecross section in another section. Any of the different types ofgeometries discussed herein can be utilized. Other discrete geometricrepresentations could also be used, e.g. specified diameters forrepresentations of the integers between 0-255 (i.e. one diameter=1 byteof 8-bit binary data), or specified diameters for a decimal encodingsystem for the integers between 0 9, or representing certain letters(e.g., a, b, c. etc.). Thus, entire bytes of data can be stored in asingle diameter, not just bits. Tolerances can be placed on thesediameters, such that small variations in diameter will not lead toerroneous measures, similar to the CMOS or TTL voltage specificationsfor microelectronics signals.

A given length can be provided for each bit or byte, similar to theclock timings of microelectronic data, and start and stop bits can becreated that have unique diameters or lengths to periodicallyre-register the length measurement so that errors do not accumulate. Ananalog method of data representation can also be implemented that canencode the equivalent to analog voltages versus time as fiber diametersversus length. Again, a calibrating start/stop bit can be used to moreaccurately read out such data. In this implementation, only a singleprecursor to manufacture the fiber may be required, although it ispossible to employ two or more precursors to provide fibers with binaryor more complex compositions. Similar analog and/or digitalrepresentations can be implemented for fibers having specificcompositions and/or coatings.

Encoding in circular or spiral patterns on fibers can also be used (ascoatings, compositions, or geometries), which can increase data density,although these can be more challenging to read-out. Another means ofachieving data encoding in fibers is to zig-zag the fibers discretely orin a gradual fashion to represent numbers. In this case, the axis of thefiber is shifted as it is grown, relative to a known reference axis, andthe distance, orientation, or angle relative to the reference axisprovides the indication of which number is represented. This approach,however, generally results in a lower encoding rate than diametermodulation.

It is important to note that a secondary heating means (in addition tothe primary means) can be used to heat the gases locally and change theoutcome of the fiber deposition in a rapid way. Thus, for instance, afocused laser beam can be combined with a heating coil; the laser beaminduces the primary growth, while the coil can change the composition,microstructure, or geometry locally by heating the fiber inductively. Inthis example, the coil could perform grain refinement to change themicrostructure, or zone refinement of a dopant within the fiber or as acoating on the fiber. Due to the small size of the fibers, theseprocesses can occur rapidly. A secondary heating means can take manyforms, including: wire(s), electrode(s), laser beams(s), etc. Severalpossible implementations of heating means are shown in FIGS. 21-24. Thesecondary heating means, if provided as a coiled wire geometry, can alsoinduce magnetic fields, which can be encoded into the orientation of thematerial within/on a growing fiber (or coating).

For example, FIG. 21 shows one embodiment of the invention using a laseras the primary heating means 40 and a wire 110 as a secondary heatingmeans 40 to create a fiber 25 where the composition of the fibers ismodulated along the lengths of fibers to record information. In FIG. 21,the fiber 25 composition is altered along its length utilizing a firstcomposition sections 410 and a second composition sections 415. One endof the fibers 25 is attached to a substrate 320, with the other end inthe reaction zone 35. The substrate 320 can optionally be detached, ifthe relative position of the fibers is maintained in some other fashion.

FIG. 22 shows an embodiment of the invention using a laser as theprimary heating means 40 to create a fiber 25 where the composition ofthe fibers is modulated (by the laser) along the length of the fibers torecord information. In FIG. 22, the fiber 25 composition is alteredalong its length utilizing a first composition sections 410 and a secondcomposition sections 415. One end of the fibers 25 is attached to asubstrate 320, with the other end in the reaction zone 35. The substrate320 can optionally be detached, if the relative position of the fibersis maintained in some other fashion.

FIG. 23 shows one embodiment of the invention using a laser as theprimary heating means 40 and a laser as the secondary heating means 40to create a fiber 25 where the composition of the fibers is modulatedalong the length of the fibers to record information. In FIG. 23, thefiber 25 composition is altered along its length utilizing a firstcomposition sections 410 and a second composition sections 415. One endof the fibers 25 is attached to a substrate 320, with the other end inthe reaction zone 35.

FIG. 24 shows one embodiment of the invention using a laser as theprimary heating means 40 and a secondary heating means 40 using a highpressure discharge heating with an electrode to create a fiber 25 wherethe composition of the fibers is modulated along the length of thefibers to record information. In FIG. 24, the fiber 25 composition isaltered along its length utilizing a first composition sections 410 anda second composition sections 415. One end of the fibers 25 is attachedto a substrate 320, with the other end in the reaction zone 35. In anyof the embodiments shown in FIGS. 21-24, varying characteristics otherthan the composition of the fiber can be utilized, for example, thegeometry of the fibers could be altered, or a coating to the fiber canbe added as described above.

One implementation that speeds up the data-encoding rate uses at leastone LMM precursor (e.g. silane, SiH4), and at least one HMM precursor(e.g. n-icosane, C20H42, or n-tetracontane, C40H82). It can also employmassive reactive gases (e.g. iodine) that are not intended to add adeposit element/compound to the reaction, but can modify themicrostructure or geometry of the fibers by their presence, e.g. theformation of sp3- vs. sp2-bonded carbon. This particular implementationemploys the thermal diffusion effect to concentrate the LMM precursor atthe thermal diffusion region 10 and reaction zone 35 discussed above.Any of the various embodiments disclosed above (e.g., FIGS. 1-11) can beutilized for recording information on fibers, including but not limitedto primary and/or secondary heating means used to control the reactionand fiber characteristics (e.g. diameter, microstructure, etc.).

In some embodiments, another aspect of the invention is that each fibermay (optionally) contain a calibration code, located at a designed placeon the fiber, that allows it to be unique from the other fibers, butenables it to be read accurately. This also provides another means ofencrypting data, and making it harder for unauthorized personnel toread-out the data. The calibration code can provide information on thetype of characteristics that are to be read, sensed, or measured todecipher the code, e.g., the electrical conductivities, dielectricconstants, thermal conductivity/capacity, optical transmittance,reflectance, and/or absorbance, or selective chemicalreactivity/bonding, dangling bonds, or wetting characteristics at thesurface of the fibers, or the length of each byte, start/stop bits,fiber diameters v. length, a calibrating start/stop bit, etc. It canalso include a code key (discussed below). The calibration code and/orcode key can be located in a pre-defined location in or along the fiberso that the calibration code and/or code key can be detected and read.

To Applicant's knowledge, sequential recording of information on or infibers has not been done prior to this invention, including recordingusing active control a plurality of thermal diffusion regions.

Any of the various embodiments disclosed above that use or implementmodulation in or around the reaction zone or thermal diffusion region orthe flow of precursor using the selective conduits or switches/valvescan be utilized for recording information on fibers. Examples of themodulation in or around the thermal diffusion region or the flow ofprecursor are shown and discussed in reference to FIGS. 9(a),(b), and 10as examples. The ability to switch the thermal diffusion valves rapidlyprovides the means for rapidly modulating the composition and/orgeometry of the growing fibers, especially where the fibers are alsogrowing rapidly on the order of millimeters per second. Thus, it ispossible to encode information into/onto the fibers as they are grown,providing a permanent or semi-permanent record of that informationsolely with the secondary heating means. This can also be done usingonly the primary heating means. Where hundreds and thousands of fibersare grown simultaneously, a parallel system of encoding/writinginformation becomes feasible. For example, where the thermal diffusionvalves are modulated at 1 ms intervals, and the fibers are 8-bitdiameter-encoded fibers growing at 2 mm/s, and 20,000 fibers are growingsimultaneously, information can be encoded/written at a rate of 320 Mbper second. This may be slower than some hard drives available today,but approaches USB data transfer rates, and can be written in a morepermanent archival form than magnetic or magneto-optical drives.

Importantly, data can be encoded on extremely stable materials, bothphysically and chemically, to preserve an archival record ofinformation. For example, in the composition-encoding approach, fiberscomprised of tantalum carbide, with a melting point of 3153-4100 K canbe encoded with variations in the carbon concentration within thedeposit of up to 2:1 (TaC versus TaC0.5). Or titanium oxide fibers canbe grown, with varying concentrations of oxygen that change the opacityof the fibers to light—and the data can be read optically. Or the samesystem can be read by measuring the dielectric constant or resistivityof the deposit versus length.

A wide variety of different LMM precursors and HMM precursors can beemployed in combination in order to obtain the desired thermal diffusionregion and controlling effects. For example, for silicon deposition froman LMM precursor, hydrides could be used, including silane and disilane.While for HMM gases, precursors such as tetraiodo methane, or waxes canbe used. This list is not intended to be exhaustive, and it is only forexplanatory purposes. For instance, there are dozens of possible siliconprecursors and wax combinations. Again, uses of LMM precursors and HMMprecursors are optional.

A device to read-out the information recorded or encoded on the fiber isalso disclosed. In some embodiments, an example of which is shown inFIG. 25, the read-out system includes a sensing means (or sensors) 450,a translation means 455 (represented by the arrows) to move the sensorsupport surface 465, holes/apertures 460 for fibers to pass through, asensor support surface 465 (e.g., some type of plane, surface or grid tosupport the sensors), and an analog/digital (“A/D”) system 470 forrecording the data for later use. The sensing means (or sensors) 450 canbe any known or future developed sensor that can sense, detect, or readthe various characteristics of the fibers discussed herein, for example,sensors or detectors that can sense, detect, read, or measure theelectrical conductivity, dielectric constant, thermalconductivity/capacity, optical transmittance, reflectance, and/orabsorbance, or selective chemical reactivity/bonding, dangling bonds, orwetting characteristics at the surface of the fibers, or the length ordiameter of the fibers. The sensing means 450 can be electricallyconnected to the analog/digital system 470 or utilize other means tocommunicate readings to the analog/digital system 470. Examples ofvarious sensing means were discussed above (and described as “feedbackmeans” in the context of fabrication of the fibers), but may bedifferent when utilized to read already-manufactured fibers than thesensing means (or feedback means) utilized for the fabrication of thefibers. The analog/digital system 470 can be computer hardware,software, or firmware that can interpret and decode the readings fromthe sensing means (or sensors) 450, and would be well understood tothose of skill in the art. For example, if differing conductivities isused for the encoded information, the analog/digital system 470 mightinterpret a reading between values A and B to be a “0” and a readingbetween values C and D to be a “1” (in a binary application). The sameis true for measurements related to dielectric constant, thermalconductivity/capacity, optical transmittance, reflectance, and/orabsorbance, or selective chemical reactivity/bonding, dangling bonds, orwetting characteristics at the surface of the fibers, or the length ordiameter of the fibers, and the other embodiments. As discussed above,any other discrete representations can be utilized and implemented bythe analog/digital system 470 , e.g., certain values or readings can beassociated with, or represented by integers between 0-255 (i.e. onediameter =1 byte of 8-bit binary data), decimal encoding for theintegers between 0-9, or representing certain letters (e.g., a, b, c.etc.). The analog/digital system 470 can have non-transitory memory, andbe programmable, storing the values, numbers, or letters associated withparticular readings from the sensing means (or sensors) 450, alsoreferred to as a “code key.” In this embodiment, the sensing means 450are on a sensor support surface 465, which has holes/apertures 460through which the fibers 25 can pass. The fibers 25 can be translated ormoved such that different portions of the fibers 25 pass by or in thedetection area of the sensing means 450. The readings from the sensingmeans 450 are then provided to the analog/digital system 470 for furtherprocessing. Obviously, other configurations for reading fibers arepossible, for example, where the fiber is passed by the sensing means450 without passing through a hole 460 in the sensor support surface465.

The various code keys (if utilized) can also be utilized in themanufacture of the fibers, and in connection with the feedback means andcontrolling means, when depositing the encoded information. Theappropriate control systems for the fiber manufacture alter theoperating parameters to encode the desired information using the codekey. For example, if differing electrical conductivity is used, the codekey might provide that an electrical conductivity between values A and Brepresents a “0” and an electrical conductivity between values C and Drepresents a “1”. If the user wants to deposit encoded informationrepresenting a data string of 010010011, the control systems of themanufacturing process (for example, the laser power, primary heatingmeans, secondary heating means, amount of precursors, flow of precursorto the reaction zone, pressure, etc.) would be manipulated to ensurethat the appropriate material is deposited at the appropriate locationsthat would trigger the appropriate a sensor reading. The code key canalso be fabricated onto the fibers themselves for reading and use by theanalog/digital system 470.

Thus, in one embodiment, a recording media is provided comprising fiberswherein the fibers have specific fiber states along the length of saidsolid fibers, the fiber states having known lengths (corresponding to atime duration of a signal), wherein values of said fiber statesrepresent digital or analog values (corresponding to signal amplitudes),and wherein the combination of said known lengths and values of saidfiber states encodes digital or analog information sequentially alongsaid solid fibers. The “fiber states” can be a variety differentcharacteristics, including (1) fiber geometries, (2) fiber diameters,(3) fiber composition, (4) fiber microstructures, (5) fibermicrostructures and fiber composition, (6) physical properties, (7)chemical properties, and (8) presence, absence, or thickness of coatingson the surfaces of said solid fibers, or any combination of theforegoing.

In the embodiment wherein the “fiber state” is fiber geometry, variousalternatives are available, including (a) the slopes of the surfaces ofsaid solid fiber relative to the fiber axis; (b) the azimuthal positionof the fiber growth direction relative to a known axis; and/or (c) theorientation of the fiber growth direction relative to a known axis.

In the embodiment wherein the “fiber state” is fiber composition,various alternatives are available, including (a) fiber compositionsinclude two or more different elements/compounds, including wherein saiddifferent elements/compounds being deposited from two or more precursorswith disparate decomposition rates versus temperature (b) fibercompositions include two or more different elements/compounds, includingwherein said different elements/compounds being deposited from at leastone multi-element-bearing precursor that yields disparateelements/compounds versus temperature.

In the embodiment wherein the “fiber state” is fiber microstructures,various alternatives are available, including where the fibermicrostructures include (a) two or more allotropes; and (b) two or moresolid phases.

In the embodiment wherein the “fiber state” is fiber physicalproperties, various alternatives are available, including optical,electrical, thermal, acoustic, physisorptive, adhesive, or mechanicalproperties.

In the embodiment wherein the “fiber state” is chemical properties,various alternatives are available, including chemisorptive, oxidative,reductive, reactive, bonding-, dandling bond-, or wetting-properties.

In another embodiment, a method of recording digital and/or analoginformation onto fibers and/or an array of fibers is provided,comprising (1) creating an array of reaction zone(s) within a vessel,wherein decomposition of at least one precursor species occurs; saidarray of reaction zone(s) being created by a primary heating means, thedecomposition resulting in the growth of solid fiber(s) at each saidreaction zone(s); (2) said solid fiber(s) having a 1st end at saidreaction zone(s) and a 2nd end that is drawn backward through atensioner 45 and spooling device/mandrel 50, at a rate to maintain the1st end within (or near) said reaction zone(s); (3) said decompositionbeing modulated over time by a controlling means to create specificfiber states versus length along the growth direction of said solidfibers; (4) said fiber states having known lengths (corresponding to atime duration of a signal); (5) wherein values of said fiber statesrepresent digital or analog values (corresponding to signal amplitudes);(6) wherein the combination of said known lengths and values of saidfiber states encodes digital or analog information sequentially alongsaid solid fibers. Thus, in some embodiments, the solid fibers can forman array that allows for massively parallel encoding of digital and/oranalog information.

In another embodiment, a method of recording digital and/or analoginformation onto fibers and/or an array of fibers is provided,comprising (1) introducing at least one low-molecular mass (LMM)precursor species into a vessel; (2) introducing at least onehigh-molecular mass (HMM) precursor species into said vessel, of masssubstantively greater than the LMM precursor species, and of thermalconductivity substantively lower than that of the LMM precursor species;(3) creating an array of reaction zone(s) within a vessel by a primaryheating means, wherein decomposition of at least one precursor speciesoccurs; (4) establishing thermal diffusive regions (TDRs) at/near saidreaction zone(s) by a secondary heating means, to partially- orwholly-separate the LMM precursor species from the high molecular massprecursor species using the thermal diffusion effect, (5) saiddecomposition resulting in the growth of solid fiber(s) at each saidreaction zone(s); said solid fibers being comprised of at least oneelement from said precursor species; (6) said solid fiber(s) having a1st end at said reaction zone(s) and a 2nd end that is drawn backwardthrough a tensioner 45 and spooling device/mandrel 50, at a rate tomaintain the 1st end within (or near) said reaction zone(s); (7) saiddecomposition being modulated over time to create specific fiber statesversus length along the growth direction of said solid fibers; saidmodulation occurring by controlling said TDRs by said secondary heatingmeans (independent of said primary heating means); (8) said fiber stateshaving known lengths (corresponding to a time duration of a signal); (9)wherein values of said fiber states represent digital or analog values(corresponding to signal amplitudes); and (10) wherein the combinationof said known lengths and values of said fiber states encodes digital oranalog information sequentially along said solid fibers.

The primary heating means can be a focused laser beam, an array offocused laser beams, inductive heating of the solid fibers,high-pressure electric discharges (e.g., plasma) and electric currentthrough the precursor(s), focused line of laser light, and anycombination of the foregoing. Other primary heating means are known tothose of skill in the art and discussed herein.

The secondary heating means can be heated wire(s), wherein said heatedwire(s) are heated resistively by flowing electrical currents throughsaid wires. The secondary heating means can also be a focused laserbeam, array of focused laser beams, high-pressure electric dischargesand/or electric current through the precursors. Other secondary heatingmeans are known to those of skill in the art and discussed herein. Insome embodiments, the heated wires can be used to “flow” by-productspecies from decomposition in the reaction zone(s). The heated wires cantake a variety of configurations, including but not limited to (a) wherethe heated wire(s) are comprised of at least two joined, butelectrically separate sections, wherein the current through one saidsection is used to modulate the flow of low-molecular mass precursorspecies in real-time to the reaction zone(s), (i.e. the said sectionacts as a thermal diffusive valve); (b) where at least one section ofsaid heated wire(s) is heated by a laser beam, and is used to modulatethe flow of low-molecular mass precursor species in real-time to thereaction zone(s), (i.e. the said section acts as a thermal diffusivevalve); (c) where at least one section of said heated wire(s) hasattached cooling fins that may be heated resistively at their base, andis used to modulate the flow of low-molecular mass precursor species inreal-time to the reaction zone(s), (i.e. the said fins act as a thermaldiffusive valve); and (d) where at least one section of said heatedwire(s) has attached dispersion wires that may be heated resistively todisperse the low-molecular mass precursor species along the thermaldiffusive conduit, and is used to modulate the flow of low-molecularmass precursor species in real-time to the reaction zone(s), (i.e. thesaid dispersion wires act as an inverse thermal diffusive valve).

In some embodiments, the vessel in which precursors are introduced canalso have a pressure controlling means as described above. As discussedabove, the species introduced into the vessel can be in various forms.In some embodiments, all species are in the gaseous state. In otherembodiments, the species concentrated at the reaction zone(s) are in thegaseous state, while all other species are in the liquid state. In otherembodiments, the species concentrated at the reaction zone(s) are at thecritical point or in the supercritical state, while all other speciesare in the liquid or solid state. In other embodiments, all species areat the critical point or are in the supercritical fluid state.

As discussed above, the sensing means (or sensors) can be used to obtainfeedback of the decomposition of the precursors and the growth of thefibers, and to control secondary heating means to control thedecomposition, growth, and composition of the solid fibers to encodedigital and/or analog information. The sensing means (or sensors) can beof a wide variety of sensing devices/spectrometers known to those ofskill in the art, including acoustical, mechanical, optical,ultraviolet, infrared, and X-ray.

In yet another embodiment, an apparatus for reading information from oneor more of an array of solid fibers is provided, wherein (a) the fibershave specific fiber states along the length of said solid fibers; (b)the fiber states having known lengths (corresponding to a time durationof a signal); (c) wherein values of said fiber states represent digitalor analog values (corresponding to signal amplitudes); (d) wherein thecombination of said known lengths and values of said fiber statesencodes digital or analog information sequentially along said solidfibers; (e) wherein said apparatus has a multiplicity of sensors locatedin a surface/grid; (f) said surface/grid having holes/passages throughwhich fibers may pass; (g) said surface/grid being translatable (forwardor backwards) along the length of said solid fibers (along the directionof fiber growth); and (h) said multiplicity of sensors beingelectrically connected to a computer or data acquisition system; whereinall said sensors can be read at a rate exceeding the Nyquist samplingcriterion as said surface is translated. In some embodiments, thetranslation can be oscillated, to obtain multiple readings of saidfibers.

Functionally-Shaped and Engineered Short Fiber and MicrostructureMaterials

In one aspect, this invention utilizes a new, highly flexiblemanufacturing process to grow short fibers from precursors. Precision,functionally-shaped, and engineered short fibers can be created throughcontrol of the process properties, e.g. heating means properties,precursor flow geometries and flow rates, local pressures, etc. asdiscussed herein. It should be noted that while the HMM precursorspecies and LMM precursor species discussed above (along with use ofthermal diffusion regions) can be used as precursors for creatingprecision, functionally-shaped, and engineered fibers, depending on thedesired characteristics of the fibers, the precursors need not share thesame characteristics discussed above with respect to the differencebetween the HMM precursor and LMM precursor. Indeed, some embodiments ofthe systems and methods for creating precision, functionally-shapedfibers and microstructures do not require use or manipulation of athermal diffusion region. Any number of systems and methods can be usedto decompose and grow fibers, including high pressure laser chemicalvapor deposition and chemical vapor deposition, hyperbaric laserchemical vapor deposition, electron beam deposition, ion beams,photolysis, and various focused energy sources.

Often, the primary heating means is a focused electromagnetic beam orother directed energy source, such as a laser, ion, or electron beam.However, other primary heating means can also be used, such as inductiveor microwave coupling into the fiber material. The primary heating meanscan be modulated, shaped, or oriented to create specific geometries inthe solid fibers as they are grown, rather than as an after-the-factadditional process that modifies existing fibers. In addition, more thanone fiber can be grown at a time by using a multiplicity of primaryheating means. For example, typical primary heating means could be anarray of focused laser beams, an array of focused laser beams and afocused line of laser light, an array of high-pressure discharges, anarray of electrodes that passes electric current through the precursors,an array of inductive primary heating means, and a set of resistivelyheated wires. And more than one primary heating means can be employed toprovide additional processing flexibility.

This invention also provides for feedback control of the desired fibercharacteristics, including shape, composition, and microstructure of thefiber materials, so that these characteristics can be controlled duringthe growth process (see FIG. 11 as one example). It provides for amethod of obtaining precise fiber lengths without using cuttingprocesses. Fibers can be grown to specific lengths, with specificdiameters vs. length, and in curvilinear patterns, rather than as juststraight cylinders. Several real-time feedback means and/or controllingmeans are used, including interferometric pattern feedback (e.g. aFabry-Perot interferometer), adaptive optic focal-plane recognition,secondary laser beam attenuation, slit imaging/sensing of fiber lengths,knife-edge and chopper techniques (e.g. attenuation or shadowgraphy),ultrasonic measurements, and thermal measurements. This is not intendedas a complete or exhaustive list.

In addition to straight (cylindrical fibers), several specific fibershapes versus length are also important for optimal composites, e.g.fibers that have sinusoidal diameter vs. length profiles (see FIG.26(a)), or other more complex geometries. These profiles can becustom-designed for specific fiber-matrix combinations. Some periodicprecision profiles that are of commercial interest are shown in FIG. 26,including (a) sinusoidal profiles vs. length (FIG. 26(a)), (b)elliptical profiles vs. length (FIG. 26(b)), (c) parabolic profiles vs.length (FIG. 26(c)), (d) hyperbolic profiles vs. length (FIG. 26(d)),(e) Gaussian profiles vs. length (FIG. 26(e)), (f) saw-toothed/ramp-likeprofiles vs. length (FIG. 26(f)), (g) dog-bone-like profiles v. length(FIG. 26(g)), and (h) bed-post-like profiles vs. length (FIG. 26(h)).Importantly, these profiles can be periodically added to straightfibers, such as the representative examples shown in FIG. 26(i) havingperiodic sinusoidal shapes, periodic elliptical shapes, periodicmulti-frequency shapes, periodic parabolic shapes, etc. Or, one or moreprofile geometries can be modulated onto another profile, creating morecomplex profiles with additional functionality. For example, asinusoidal variation can be superimposed on a hyperbolic profile—i.e. asinusoidal hyperbolic geometry—to create a fiber such as that shown inFIG. 26(j); this fiber would have high pull-out strength due to thedog-bone shape (one would have to shear off the protrusions for it toslip) and at the same time have increased surface area due to thesinusoidal variations which creates additional adhesion at theinterface. Lastly, arbitrary profiles, with randomized diameters can becreated (FIG. 26(k)), which provide for statistical randomization ofadhesion of a fiber within its matrix (or randomization of otherproperties). Even simple fractal profiles are possible, where at leastone pattern repeats at different length scales (see FIG. 26(l)).Additional variable shapes can also be combined, as shown in FIG. 26(m).

In addition, the cross-sections of fibers need not be circular, butcould be grown in a wide-variety of shapes shown in FIG. 27. Forexample, the cross-section could be that of an I-beam (FIG. 27(a)),X-beam (cross) (FIG. 27(b)), L-beam (FIG. 27(c)), T-beam (FIG. 27(d)),or a star-like shape (namely a multi-pointed star and/or a multi-pointedstars with T-like points) (FIG. 27(e)). Further, circular (FIG. 27(f)),elliptical, triangular (FIG. 27(g)), rectangular (FIG. 27(h)), hexagonal(FIG. 27(i)), polygonal, arbitrary (FIG. 27(j)) and/or modulated (FIG.27(k)) cross sections can be grown. This is not intended as anexhaustive list of different cross sections that can be utilized. Thiscan potentially increase the strength-to-mass ratio of the reinforcingfibers in desired directions.

In addition, the growth direction of the fibers can be reoriented duringdeposition in a continuous fashion to create geometries not possiblethrough any spinning or extrusion process. Just as examples, theposition of the reaction zone can be altered (as described herein) orthe substrate on which the fibers are being grown can be moved orreoriented. There are many possible shapes induced by reorientation andshown in FIG. 28: FIG. 28(a) shows a curvilinear shapes, FIG. 28(b)shows a gentle curves, FIG. 28 (c) shows sinusoidal shapes, FIG. 28(d)shows parabolic shapes, FIG. 28(e) hyperbolic shapes, FIG. 28(f)U-shapes, etc. These curvilinear shapes make for fibers that are grownwithout residual stresses in a desired shape, but that are verydifficult to “pull-out” in any direction. As also shown in FIG. 28, itis possible to create fibers with “hooks” or “barbs” that will interlockwith other fibers within a composite, transferring local stresses fromone fiber to the next (see FIG. 28(g) for hooked shape & 28(h) forbarbed shape). To further increase pull-out strength, zigzag fibers(FIG. 28(i)) and ramp-like fibers (FIG. 28(j)) can be grown. An exampleof zigzag fibers grown is shown in FIG. 33. In another embodiment,coiled fibers are generated that will be more flexible than a simplelinear cylinder of given Young's Modulus in the same volume (and thathave more surface area), potentially providing a route to stronger,tougher, and more flexible composite materials (see FIG. 28(k)). Andfinally, more than one pattern may be superimposed in the orientationgeometry, thereby creating modulated orientations (FIG. 28(l)).

Even more complex shapes can be created by changing the intensity of theprimary and/or secondary heating means, even as it is reoriented. Forexample, a complex curved fiber can be created with periodic undulationsalong its length (see FIG. 29). And it is possible to change thecross-sectional shape, even as cross-sectional size and orientation ofthe fiber is changed.

Another aspect of this invention is that it inherently provides sub-100nanometer local smoothness in the surfaces that are grown, allowing forimproved bonding at the fiber-matrix interface (e.g. through Van DerWaals or Covalent bonding). This can be improved to even greaterprecision through feedback control of the primary and/or secondaryheating means and other process parameters during the growth process asdescribed above. The carbon fiber shown in FIG. 30 is an example of afiber grown with sub-100 nanometer local surface smoothness. Because thefibers are not pulled through any mechanical spinning or drawingprocesses, they exhibit very few (if any) voids/cracks, and the materialcan be grown as a fully dense material. In addition, the materialmicrostructure can be designed to be amorphous or glassy, which willgive strong fibers that have more uniform properties. The materialmicrostructure can also be that of single-crystal fibers/whiskers, whichmay have much greater strength than polycrystalline forms of the samematerial.

Another aspect of the invention is that multiple materials can be grownsimultaneously to create a functionally-graded fiber. For instance,where two materials are deposited at the same time under a Gaussianlaser focus, with different threshold deposition temperature andkinetics, one material will naturally be more highly concentrated in thecore of the fiber, while the other tends to grow preferentially towardthe outside of the fiber. However, rather than having a distinct steptransition from one material to another, as would be present in acoating for example, they can be blended together with a gradualtransition from core to outer material. This can create a strongertransition from core to outer material that will not separate. Thispermits a very strong material that might otherwise react or degrade incontact with the matrix material to be permanently protected by anexterior material that contacts the matrix material. This canpotentially improve bonding between fiber and matrix materials, allowfor flexible transitions between fiber and matrix, and preventundesirable alloying or chemical reactions. There are many possibleimplementations of this multiple material approach, and the fibers canbe functionally graded radially and axially. The method for applying theprecursors can also vary. For example, they can be flowed pre-mixed orseparately to create anisotropic variations in composition (see FIG.31). FIG. 31(a) depicts a radial blend of the deposited materials, shownas a cross section of a fiber. In this embodiment, a first material 280is concentrated at the fiber core, while a second material 285 isconcentrated outside of the core. In most cases, there is a gradualtransition portion 290, such that as you move away from the core, thedeposited material transitions from the first material 280 to the secondmaterial 285. Additional materials could also be deposited in thisfashion having a radial blend of multiple materials.

FIG. 31(b) depicts an axial blend of the deposited materials. In thisembodiment, a first material 280 is deposited as the fiber. The fiberthen has a transition portion 290, where the fiber transitions to asecond material 285. Again, additional materials could be deposited.FIG. 31(c) depicts an anisotrophic blend of the deposited materials. Inthis embodiment, a first material 280 is deposited in one portion of thecross section of the fiber, while a second material 285 is deposited ona separate portion of the cross section of the fiber, with a transitionportion 290 separating the two materials. It should be noted that thetransition portion 290 is optional, and may not be needed depending onthe desired fiber characteristics, precursors used, heating conditions,etc.

Importantly, fibers can also be branched to create additional resistanceto fiber pull-out. Fibers can form networks of connected strands, anexample of which is shown in FIG. 32. The branched fiber shown in FIG.32 was created using two primary heating means (laser beams)overlapping, and then moving them apart during growth to separate thereaction (or growth) zone into two reaction zones.

In some embodiments, the invention also provides for a means ofcollecting and removing the fibers following their growth, with optionalrecirculation or re-use of an initial substrate (see FIG. 34(a)-(d)).The term “substrate” is here used loosely, and includes wires, wiremeshes, plates, wafers, flexible films, discs, drums, belts, coils, etc.For example, in one implementation, fibers can be grown on a substratethat has minimal adhesion to the growth material (i.e., the fibers), anda wiper blade can be used to “knock” the fibers from the substrate (FIG.34(a)). In FIG. 34 (a), a spinning mandrel or drum 300 is shown on whichthe fibers are grown. The primary and secondary heating means can usethe systems and methods described above to control the reaction zone 35and other parameters of fiber growth. The embodiment shown in FIG. 34(a)shows a plurality of primary heating means 40 (lasers in thisembodiment) growing a plurality of fibers. As the mandrel/drum 300spins, the grown fibers 25 are rotated toward the wiper 310, detachingthe fibers from the substrate, where they can be collected in a fiberbin 315. The movement of the mandrel/drum 300 can be controlled by thecontrolling means discussed above utilizing conventional industrialequipment.

In another embodiment, shown in FIG. 34(b), fibers 25 can be grown on amoveable substrate 320, for example, one that moves vertically up anddown, or that can vibrate, and with a wiper 310 or knife edge that“cleaves” them from the substrate 320. The moveable substrate 320 may bea drum or belt, or any other suitable configuration, including astand-alone substrate as shown in FIG. 34(b) (for example, one that isnot “continuous” like a belt or drum). Manufactured fibers 25 can alsobe collected in a fiber bin 315.

In another embodiment shown in FIG. 34(c), fibers 25 can be grown on aflexible substrate 320 configured as a belt that translates and rotates.The movement of the belt can be controlled by the controlling meansdiscussed above utilizing conventional industrial equipment. The beltcan be stopped (if needed) and fibers 25 grown in one or more reactionzones, and/or the heating means can also be moveable or redirected in amanner such that as the flexible substrate 320 moves, the heating meansmove or are redirected to maintain the appropriate reaction zone wherethe fiber is growing. When the desired growth is completed, the fibers25 can be removed. In some embodiments, the rotation of the flexiblesubstrate 320 around the end of the belt can drop the fibers 25 (asshown in FIG. 34(c)), or a wiper 310 or knife edge can be used (notshown).

In another embodiment, fibers can be grown on a wire, and the wire(ultrasonically) vibrated following growth to remove the fibers. Inanother embodiment, the fibers can be removed by flowing a fluid acrossthe fibers. In another embodiment, electrostatic forces can be used toremove the fibers from the surface. Finally, in another embodiment, atemporary coating can be dissolved away from the substrate, removing theattachment point for the fibers.

In another embodiment, shown in FIG. 34(d), fibers 25 can be removed bycentrifugal forces. In FIG. 34(d), a spinning mandrel or drum 300 isshown on which the fibers are grown. The heating source, reaction zoneand other parameters of fiber growth can be using the systems andmethods described above. The embodiment shown in FIG. 34(d) shows aplurality of primary heating means 40 (lasers in this embodimentdirected through a window 330 in the reaction vessel) growing aplurality of fibers 25. As the mandrel/drum 300 spins, the centrifugalforces remove the grown fibers, where they can be collected in a fiberbin 315. The movement of the mandrel/drum 300 can be controlled by thecontrolling means discussed above utilizing conventional industrialequipment. There are many possible implementations for removing fibers.It will be understood by those of skill in the art that the substrate onwhich the fibers are being grown can move or remain stationary duringfiber growth. If the substrate is moving during fiber growth, theheating means can be moveable or redirectable as needed to maintain thereaction zone for fiber growth.

Following removal, the short fibers can be collected in a bin and thensuctioned from the growth system with a vacuum or similar device. Inanother embodiment, fibers can pass through a vapor lock that preventsthe precursor from leaving the reaction vessel, but moves the solidfibers through another fluid to the outside of the growth system. Inanother embodiment, fibers can be collected in a bin and removed througha traditional load-lock. There are many possible means of collecting andremoving fibers in bulk; this is not intended as an exhaustive list.

It is also possible to utilize a reusable substrate in the form of atape, mesh, or lattice onto which the fibers are grown. This substratemay be flexible, which can be coiled up and stored for later use, asshown in FIG. 35. This roll could then be applied directly into acomposite matrix material or cut/stacked and infiltrated with a matrixto create novel interwoven composite materials with fibers crossing theplane of the substrate.

Thus, in one embodiment of the invention, an engineered solid fibermaterial can be grown from fluid-based chemical precursors by a heatingmeans that is less than 4 mm in cross-sectional extent/diameter, that isgrown to a prescribed length, that has a prescribed cross-sectionalfiber shape and size that can vary along its length, that has aprescribed composition versus radius, that has a prescribed geometricorientation versus its length, and that has a prescribed microstructure.

As described above, in some embodiments, the cross-section of the fibercan be circular, elliptical, triangular, X-shaped (cross), I-shaped,L-shaped, T-shaped, multi-pointed star, multi-pointed stars with T-likepoints, rectangular, hexagonal, polygonal, arbitrary, and/or modulatedcross-sections. The cross-sectional fiber shape may vary along itslength or it may be constant. In some embodiments, the cross-sectionalfiber shape may vary along its length and repeat periodically. In someembodiments, the cross-sectional fiber shape varies along its length,and repeats periodically, and the cross-sectional fiber shape is acomposite of two or more repeating profiles, and where at least oneprofile is modulating another. In some embodiments, the cross-sectionalfiber size varies along its length while in others the fiber size isconstant along its length. In some embodiments, the cross-sectionalfiber size varies along its length, forming a profile that is selectedfrom at least one of the following: (a) sinusoidal, (b) elliptical, (c)parabolic, (d) hyperbolic, (e) Gaussian, (f) saw-toothed/ramp-like, (g)dog-bone-like shapes, and (h) bed-post-like shapes. In some embodiments,the cross-sectional fiber size varies along its length and repeatsperiodically, forming a repeating profile that includes at least one ofthe following profiles: (a) sinusoidal, (b) elliptical, (c) parabolic,(d) hyperbolic, (e) Gaussian, (f) saw-toothed/ramp-like, (g)dog-bone-like shapes, and (h) bed-post-like shapes. In otherembodiments, the cross-sectional fiber size varies along its length andrepeats periodically, forming a repeating profile that includes linearsections with at least one of the following profiles: (a) sinusoidal,(b) elliptical, (c) parabolic, (d) hyperbolic, (e) Gaussian, (f)saw-toothed/ramp-like, (g) dog-bone-like shapes, and (h) bed-post-likeshapes.

In some embodiments, the cross-sectional fiber size varies along itslength and repeats periodically at more than one frequency, forming acomplex multi-frequency repeating profile. In some embodiments, thecross-sectional fiber size varies along its length, forming a profile,and repeats periodically, and whose profile is a composite of two ormore repeating profiles, and where at least one profile is modulating(or superimposed upon) another. In some embodiments, the cross-sectionalfiber size varies randomly along its length, forming an arbitraryprofile that does not repeat any particular pattern. In someembodiments, the cross-sectional fiber size varies along its length andrepeats periodically, and whose profile has self-similar repeatingprofiles at different length scales (a fractal profile).

As described herein, the composition of the fibers can be varieddepending on the desired characteristics. Thus, in some embodiments, theprescribed composition versus radius is a constant. In some embodiments,the prescribed composition versus radius varies from one or more corematerials in the fiber center to one or more outer materials at theouter surface of the fiber. In some embodiments, the prescribedcomposition versus radius varies continuously from one or more corematerials in the fiber center to one or more outer materials at theouter surface of the fiber, according to a prescribed concentrationfunction. In some embodiments, the composition is a radial blend fromcore material(s) to outer material(s). In some embodiments, thecomposition is an axial blend from one material to another material. Insome embodiments, the composition changes along a directionperpendicular to the axis of said solid fiber (e.g. a bi-morph).

As described herein, the microstructure of the fiber can be varieddepending on the desired characteristics. Thus, in some embodiments, theprescribed microstructure of the fiber is amorphous or glassy. In someembodiments, the prescribed microstructure is a single crystal.

As also described herein, the orientation of the fiber can be varieddepending on the desired characteristics. Thus, in some embodiments, theprescribed orientation changes along said fiber material's length. Insome embodiments, the prescribed orientation changes along said fibermaterial's length according to at least one of the following patterns: acurvi-linear shape, a gentle curve, a sinusoid, a parabola, a hyperbola,a U-shape, hooked shapes, barbed shapes, zigzag-like shapes, ramp-likeshapes, coiled shapes, and modulated shapes. In some embodiments, thefiber material branches (or divides) from one fiber into two or morefibers during growth. In some embodiments, the fiber material is locallysmooth to better than 500 nm RMS roughness over at least 5 microns oflength. In some embodiments, the fiber material is grown to apre-scribed length, to better than 5 microns accuracy.

In another embodiment, the invention relates to a method for growing oneor more engineered solid fibers from a chemical precursor within areaction zone. The fibers may be grown on a reusable substrate. Thesolid fibers may have a first end, and at least one second end, saidfirst end being attached temporarily at the reusable substrate(s), saidsecond end(s) being within said reaction zone(s). The reaction zone canbe created by a primary heating means and optionally a secondary heatingmeans. In some embodiments, the reaction zone can be modulated andcontrolled in real-time, thereby generating specific fibercross-sections, profiles, and geometric orientations versus length. Thespecific fiber cross-sections, profiles and geometric orientationsversus length can be monitored in real-time by a monitoring system (orfeedback means), and used to control the manufacturing process andproperties of the reaction zone(s). The length of said solid fibers mayalso be monitored in real-time by a monitoring system (or feedbackmeans), and used to control the manufacturing process and properties ofthe reaction zone(s), thereby growing said solid fibers to predeterminedterminal lengths. The fibers may be detached and collected after growthfrom the substrate(s) by a collecting mechanism and the substrate(s) maybe recycled/reused for the growth of additional solid fibers, forexample, by a recycling mechanism (e.g., a rotating drum or belt).

As described above, the precursor can be in various forms, includinggaseous fluids, liquid fluids, critical-fluids, or supercritical-fluids.The substrate is preferably reusable, and preferably has a texture,composition, or surface coating that provides sufficient adhesion duringgrowth to secure a first end to the reusable substrate, while havingsufficiently limited adhesion to allow said first end to be removed by acollecting mechanism (e.g., a wiper or knife-blade). The substrate canbe of various forms, including but not limited to a wire, wire mesh,plate, wafer, flexible film, disc, drum, belt, helical coil, etc.

As described herein, in some embodiments, the reaction zone(s) can besplit, thereby creating additional second end(s) for each fiber, whichare branched off each fiber. The primary heating means can be any of theheating means discussed above, including but not limited to an array offocused laser beams, an array of focused laser beams and a line offocused laser light, two or more arrays of focused laser beams,high-pressure discharges, electric current through said precursors,inductive heating, coupled electromagnetic radiation, and/or aresistively heated wire.

As described herein, in some embodiments, the properties of the reactionzone can be altered using the systems and methods discussed above,including but not limited to the shapes, sizes, positions, and geometricorientations of the reaction zone(s), as well as the reaction ratesacross said reaction zones. In some embodiments, the reaction zones arecreated, modulated, and controlled in real-time, by (1) a primaryheating means, (2) the flow rate of said chemical precursor(s), and (3)the local concentration of said chemical precursor(s), therebymodulating the cross-sectional shape, size, composition, andmicrostructure of said second end(s) in real-time to achieve specificfiber cross-sections, profiles, geometric orientations, compositions,and microstructures versus length.

In some embodiments of the method for growing the fibers, thecross-sections of the fiber(s) are controlled to desired size with atolerance of better than 500 nm over a 5 micron length, terminal lengthis accurate to 5 microns or less, and fibers can have any of thecross-section shapes, profiles, geometric orientations, compositions,and variations described above (e.g., varying along the fiber's length,or constant, repeating or arbitrary, etc.).

In some embodiments, the reaction zones are also modulated andcontrolled in real-time by a secondary heating means, as describedabove, which may be, but is not limited to, at least one heated wire,which is heated resistively, inductively, or through coupledelectromagnetic radiation.

In some embodiments, the reaction zones may also be modulated andcontrolled in real-time by introducing at least one high molar massprecursor and at least one low molar mass precursor, where this mixturewill at least partially separate in the presence of a thermal gradientwithin the reaction zone; thereby modulating the reaction rate acrosssaid reaction zone when either the thermal gradient or the concentrationof either precursor is changed. It should be recognized that the use ofhigh molar mass precursors and low molar mass precursors as describedherein is not required to create the functionally shaped and engineeredfiber described herein.

In some embodiments, the monitoring system (or feedback means) isselected from at least one of the following: interferometric patternmeasurements (e.g. a Fabry-Perot interferometer), adaptive opticfocal-plane recognition, secondary laser beam attenuation, slitimaging/sensing of fiber lengths, knife-edge and chopper techniques(e.g. attenuation or shadowgraphy), ultrasonic measurements, and thermalmeasurements (e.g. thermal conduction to sensors in the substrate).

In some embodiments, a collecting mechanism is used to detach the solidfibers from a reusable substrate. The collecting mechanism (or“collecting means”) can take a variety of forms, including but notlimited to: (1) translation and/or rotation of said reusable substrate,thereby driving said solid fibers against a wiper/blade, (2) moving awiper/blade across said reusable substrate, (3) flexing a flexiblesubstrate, (4) vibrating/shaking the substrate, (5) spinning thesubstrate to create centrifugal forces to remove said solid fibers, (6)flowing a fluid across said substrate which carries the solid fibersaway, (7) using electrostatic/magnetic forces to remove the fibers, and(8) dissolution/etching of temporary coatings on said reusablesubstrate.

In some embodiments, a recycling mechanism can be used to cause thereusable substrate to be translated, rotated, or reoriented after abatch of said solid fibers are grown to bring said reusable substrateback into alignment with said reaction zone(s) to grow additional solidfibers. In some embodiments, the recycling mechanism causes the reusablesubstrate to be coated with a temporary coating after a batch of saidsolid fibers are grown, to grow additional solid fibers on saidtemporary coating. The recycling mechanism can take a variety of forms,including but not limited to: (1) collection in a bin and removal with aload-lock, (2) collection in a bin/tube and suction with a flowingfluid, (3) collection in a filter using a flowing fluid, (4)electrostatic collection on charged materials, (5) magnetic collectionusing magnetic materials/devices, and (5) using Van Der Waals forces andcollection surfaces with high surface areas.

The substrate can be reusable in some embodiments. In some embodiments,the reusable substrate is a flexible tape or lattice that can be coiledin such a manner that said solid fibers remain on said flexiblesubstrate and can be rolled up and stored for direct or indirect use incomposite lay-ups.

Beam Intensity Profiling and Control of Fiber Internal Microstructureand Properties

A means of controlling both the beam intensity profile and shape of thethermal diffusion region can be important for obtaining desiredmicrostructures for high-quality fiber. This portion of the inventionfocuses on creating useful primary heating means intensity profiles thatwill give useful fiber properties.

There are many beneficial intensity profiles that can be generated.FIGS. 36, 38, 39, and 40 provide some examples. The simplest intensityprofiles are those known to those practicing the art of beam shaping andholography: single and multimode Gaussian beams, inverse Gaussian beams,Bessel beams, Laguerre-Gaussian beams, flat-top beams, super-Gaussianbeams, etc. In addition, these intensity profiles can be superimposed onoverall beam focal-spot geometries, e.g. circular (donut-shaped) beams,line-shaped beams, rectangular-shaped beams, cross-shaped beams, etc.

There are many ways, some known to those skilled in the art, some lessso, that can be used to generate desired beam intensity profiles forfiber growth. Methods included in this invention are: refractive andreflective field mappers that employ controlled phase-frontmanipulation, gratings and diffractive optics, vortex beam shapers,superposition of diode-laser beamlets, microlens diffusers, adaptiveoptics, spatial light modulators, liquid crystal modulators, etc. Thisis not intended as an exhaustive list.

Now, the incident (laser) beam intensity profile can, through heattransfer, influence the temperature rise at the fiber surface within thereaction zone 35, as well as the shape of the thermal diffusion region10. For example, a circular laser intensity profile can heat a fiber tipat its periphery, yielding a reaction zone that is hotter at theperiphery than in the center, and a thermal diffusion region that ishottest in a ring within the surrounding fluid near the fiber periphery.In contrast, a Gaussian beam intensity profile would yield the thermaldiffusion region that is hottest in the center. By using a circularlaser intensity profile, the thermal diffusion effect drives theby-products of reaction, not to the center of the fiber, but to itsedges, allowing the fiber to grow more rapidly in the center. Thisremoves the TDGS described previously.

For example, as shown in FIG. 36, a laser beam 500 can pass throughfocusing lens(es) 505 to create a focused profiled laser beam 510,resulting in a beam intensity profile 515 at its focal point. The beamintensity profile 515 has associated induced temperature rises atsurface 520, where the most intense portions of the laser beam profileare associated with higher temperature rises at the surface. The beamintensity profile 515 shown in FIG. 36 is an example of a particularlyuseful beam profile (a circular profile), as it can change the locationswhere certain phases will occur in a fiber. In the example of carbonfiber growth shown in FIG. 36, the resulting fiber 25 may have amorphouscarbon 525 in the core and graphitic carbon 530 around the edges (orperiphery). As discussed herein, this is in contrast to the morphologyof a fiber grown using a Gaussian beam profile, which would result in agraphitic core in its center, and more fined-grained phases on itsperiphery. Thus, one would expect the circular beam intensity profile toprovide for stronger fiber material properties than that provided by aGaussian beam intensity profile.

One subset of such a circular profile is a Bessel-shaped beam, which canbe described by a Bessel function of the first kind. Only mode 1 isshown in FIG. 36, but additional modes could be used.

Most embodiments of the invention utilize such beam profiles/shapes forthe first time to grow three-dimensional fibers by HP-LCVD, wherein themicrostructure of the fibers are controlled to provide optimal materialproperties. It should be also noted that by varying the beam profile asa fiber grows, one can also induce phase and compositional changes thatcan be used for recording information (as discussed in another sectionof this application).

Consider the three fibers shown in FIGS. 37(a)-(c), which show scanningelectron micrograph cross-sections of carbon fibers grown using threedifferent axi-symmetric beam profiles: FIG. 37(a) shows a carbon fibergrown under a focused Gaussian beam intensity profile. This fiber has agraphitic central core and outer coating. The graphitic core is composedof parabolic sheets of graphite, whose central axes align parallel tothe fiber axis. This provides little strength laterally or on axis, asthe parabolic sheets can be sheared across the fiber axis from eachother, or pulled apart along the axis. The outer coating is fine-grainedcarbon that has improved strength, but comprises little of the fibercross-sectional area. The result is a fiber that has a poor tensilestrength of only 0.598 GPa. FIG. 37(b) shows a carbon-fiber grown undera near-flat-top beam intensity profile. This also results in a core andouter fiber shell. However, now the graphitic planes are no longerextreme parabolas, but only slightly-bowed sheets that lie in planesperpendicular to the fiber axis. This orientation of the graphite alsoprovides little strength along the fiber axis. The outer coating isfine-grained, but this again comprises little of the fibercross-sectional area. The result is a less than optimal tensile strengthof the fiber that is only 0.377 GPa. Finally, FIG. 37(c) shows thecross-section of a carbon fiber grown using a circular beam profile.This again results in a two-phase fiber, with an inner core and outershell. However, now the graphite in the outer shell is lined-up co-axialto the fiber axis, and the fiber core is more fine-grained carbon. Thisprovides a carbon fiber with greatly improved strength; we recentlytested a carbon fiber with a tensile strength of 2.5 GPa, which issufficient to find utility in the high-strength carbon fiber industry.This is 4-6-times the strength of the flat-top and Gaussian profiles.This demonstrates how the specific primary heating means intensityprofiles can provide improved microstructural properties and phases ofmaterial within a fiber that makes the difference in the commercialutility of the fiber.

Similarly the strength of silicon carbide fibers grown by this techniquecan vary greatly depending on the beam intensity profile. This isbecause SiC can be grown in three phases: amorphous SiC, β-SiC, andα-SiC, in order of increasing deposition temperature. Hence, where theinduced temperature rises at the surface can cross phase boundaries, onewill generate two or more phases in a SiC fiber. As the strength ofthese phases are not the same (nor even isotopic for the crystallinephases), the value of the SiC fiber for fiber reinforcement depends onhow well the primary heating means is profiled. This is true not only ofcarbon and SiC fibers, but most materials, especially binary, ternary,quaternary, and more complex compounds/alloys.

In this invention, we offer several new methods of generating usefulprimary heating means intensity profiles/geometries for fiber growth.Examples can be seen in FIG. 38-40.

In the embodiment shown in FIG. 38(a), a Laguerre-Gaussian in the 2, 1mode is focused by the focused profile laser beam 510 onto the fiber tip495, generating the beam intensity profile 515 and induced temperaturerises at surface 520 shown. This beam intensity profile 515 is usefulfor generating a multi-phase fiber with different phases aligned withthe fiber axis. For instance, if a carbon fiber is grown, it coulddisplay graphitic carbon 530 layers on the outer layer and an innerlayer, both aligned with the fiber axis, as shown, separated byamorphous carbon 525 or fine-grained carbon. This can provide additionalstrength to such a fiber. Alternatively, two or more beam modes can becombined from different beams to create a similar intensity profile. Inthe embodiment shown in FIG. 38(b), two means of superimposing two ormore beams 500 with different beam intensity profiles 515, to create asimilar beam intensity profile 515 to that in FIG. 38(a). In this case,beam #1 is a focused Laguerre-Gaussian (Mode 1, 0) beam, while beam #2is a Laguerre-Gaussian (mode 2, 0) beam. By superimposing these two beamintensity profiles 515, we have created a dual-ring intensity profile atthe focus (also referred to as a composite beam intensity profile),which can provide the multi-phase fiber described above.

The embodiment shown in FIG. 39 depicts how superposition of manybeamlets 540 can be used to approximate a more complex profile. Whileonly 8 laser spots are created by the beamlets 540 as shown in thisfigure, the number of beamlets 540 can be increased until a nearlyuniform “ring” is created. Heat transfer within the fiber tip 495 and inthe reaction zone will tend to spread the energy deposited by eachbeamlet 540, which will tend to smooth the induced temperature rise atsurface 520 (as shown). This technique is very amenable to the use ofdiffractive optics 545, microoptics, and spatial light modulators forgenerating the beamlets. As shown in FIG. 39, one or more lenses 505 ordiffractive optics 545 can be used.

In addition, very rapid scanning of one or more “micro beamlets” onto afiber surface can simulate a complex beam profile over an extended area.In this case, the time for the surface to cool below the depositionthreshold should be much longer than the repetition rate of the microbeamlet pattern. A pulsed laser can also be used, so long as therepetition rate is sufficient.

FIG. 40 shows one possible implementation with three examples ofincident beams: (a) a first beam 560 incident at the fiber tip passingthrough a focusing lens 505, which generates a reaction zone and uses aflat-top beam intensity profile 515, (b) a second beam 565 incident onthe fiber using a beam splitter 590, but with a beam intensity profile515 that allows it to be focused on the sides of the fiber at somedistance from the first beam 560. This second beam 565 can be co-axialwith the first beam 560 or at some angle. A third beam 570 can be usedthat is incident on the sides of the fiber (using a circular beamintensity profile 515) at some distance from first beam 560 and/orsecond beam 565, that can modify the fiber material structure or addcoatings 420 to the fiber surface, and can use focusing reflective orrefractive optics 585. The third beam 570 can provide symmetric axialheating to create coatings 420 or surface modifications. The third beam570 in this embodiment uses a flat-top beam intensity profile 515. Inthe case of coatings 420, an optional aperture 575 is provided, so thatthe gases in front of the aperture (for the first beam 560 and secondbeam 565 induced reaction zones) can be different than those behind theaperture 575, allowing a different material to coat the fiber than theoriginal fiber material grown by the first beam 560 or second beam 565(as FIG. 40 shows two different coatings 420). Optional nozzles 580 orgas delivery means are provided to supply precursors to the respectivereaction zones. The optics 585 that provide the third beam 570 can bereflective (as shown), refractive, or diffractive. In all three cases ofthe first beam 560, second beam 565, and third beam 570, different beamintensity profiles 515 (each having an associated induced temperaturerise at surface 520) can be used to obtain optical material phases,microstructures, and properties. This example is provided not to beexclusive of the various possible implementations, but to show howmultiple beams, each profiled, when used in concert, can provide adeposition system sufficiently sophisticated to replace multi-step fiberextrusion/spinning, baking, and coating systems that are common inindustry today. Within a few millimeters of the initial reaction zone ofthe first beam 560, the fiber has already reached its final structureand form. Other implementations could use alternative primary heatingmeans (than a focusing laser beam), use a multiplicity of each of thevarious incident beams 560, 565, 570 discussed above, and use variousorientations and profiles to obtain the desired surface topology,internal microstructure/phases, and fiber material properties. Theseprofiled beam examples can also be used to modify the thermal diffusionregion at each reaction zone, in order to obtain optimal growth rates,correct coating thicknesses, etc. And, of course, each of these can bemodulated in real-time to obtain patterned and modulated fibers, asdescribed elsewhere in this application. The embodiment shown in FIG. 40has a core material of amorphous carbon 525.

Remember, a secondary heating means can also be used in conjunction withall of the profiled laser beam methods described herein. A secondaryheating means can also, through heat transfer, potentially influence thetemperature profile on the fiber surface. For example, a wire coilsurrounding a fiber (as in FIG. 8(b)), if held closely to the fiber, canraise the overall temperature of the fiber, thereby reducing the powerneeded by the primary heating means to induce growth.

Thus any fiber deposition system is preferably designed to optimize theprimary heating means profile/geometry (e.g. a focused beam) andsecondary heating means geometry/profile (e.g. a conductive wireassembly). In addition, their placement on the fiber can be important.In many embodiments, these are used in concert to control both thereaction zone(s) and thermal diffusion region(s).

In some embodiments, a reaction zone is created within a reaction vesselto decompose at least one precursor, the decomposition resulting growthof a solid fiber in the reaction zone. The reaction zone is induced by atemperature rise at the surface being generated by a primary heatingmeans and the temperature regions being controlled to have specificinduced temperature rise at surface versus position and time at thesurfaces of the solid fibers and within the solid fibers. As such, thefibers can be grown having specific microstructural properties bycontrolling the induced temperature rise at surface.

In some embodiments, the microstructural properties can be uniformacross any cross section of the fibers. The cross section can also havetwo or more microstructural properties, and arranged to give desiredphysical and/or chemical properties, e.g., Young's moduli, Poisson'sratios, tensile strengths, compressive strengths, shear strengths,corrosive resistance, and/or oxidation resistance of the solid fiber.

In some embodiments, the fibers can be comprised of at least 60 atomicpercent (at. %) carbon.

Various embodiments use specific beam intensity profiles versus radialposition (to create induced temperature rises at the reaction zones),which can be approximately represented by functions with the followingshapes: (a) flat top contours, (b) contours with central minima, (c)contours with a central depression and local central peak, (d)multiple-ring like shapes, and (e) toroidal shapes. The specific inducedbeam intensity profiles versus radial position can also be approximatelyrepresented by superpositions of the following functions: (a) Sinusoidalfunctions, (b) polynomials, (c) Bessel functions, (d) Laguerre-Gaussianfunctions, (e) associated Laguerre Polynomials, (f) and Hermite-Gaussianfunctions. Various modes of these above beams (functions) can be usedsolely or in concert to generate a desired intensity profile andtemperature rise at the surface. For example, the beam intensityprofiles can be generated from multiple Gaussian beam intensityprofiles, superimposed to obtain a more globally-even temperaturedistribution.

The use of laser beam profiling to enhance fiber and microstructurefabrication can be implemented in any of the embodiments discussedherein, including use of LMM precursors, HMM precursors, and thermaldiffusion regions. It can also be implemented for use in recordinginformation on or in fibers and microstructures and the functionallyshaped and engineered fibers. Thus, in one embodiment, a LMM precursorand a HMM precursor having substantially disparate molar masses areintroduced into a reaction vessel, wherein the HMM precursor also has athermal conductivity substantially lower than the LMM precursor. Athermal diffusion region is created at or near the reaction zone topartially or wholly separate the LMM precursor from the HMM precursorusing the thermal diffusion effect, thereby concentrating the LMMprecursor species at the reaction zone, and enhancing the growth of thesolid fiber, and the HMM precursor species decreasing the flow of heatfrom the reaction zone relative to that which would occur using the LMMprecursor alone. The thermal diffusion region can be at least partiallycreated by an array of focused laser beam, with the focused laser beamsare in the shape of a ring, with a maxima in a circle, and a localminimum in the center. Any of the laser beam profiles discussed hereincan be used.

What is claimed is: A method of fabricating fibers, comprising: a. introducing a low molar mass precursor species into a reaction vessel, wherein the low molar mass precursor species comprises carbon; b. introducing a high molar mass precursor species into said reaction vessel, the high molar mass precursor species having a molar mass at least 1.5 times greater than the low molar mass precursor species; c. creating (i) a reaction zone within the reaction vessel and (ii) a thermal diffusion region at or near the reaction zone, wherein at least one of the thermal diffusion region and reaction zone is at least partially created by a primary heating means, and the thermal diffusion region at least partially separates the low molar mass precursor species from the high molar mass precursor species and concentrates at least one of the precursor species at the reaction zone, wherein the at least one of the precursor species concentrated at the reaction zone is in the gaseous phase; and d. producing a solid fiber from the at least one precursor species concentrated at the reaction zone, wherein the solid fiber comprises carbon.
 2. The method of claim 1 wherein the precursors are premixed before flowed into the reaction vessel.
 3. The method of claim 1 wherein the microstructural properties of the solid fiber are generally uniform across a fiber cross section.
 4. The method of claim 1 wherein the primary heating means is a laser.
 5. The method of claim 1 wherein the precursors are premixed before flowed into the reaction vessel, the microstructural properties of the solid fiber are generally uniform across a fiber cross section, and wherein the primary heating means is a laser.
 6. The method of claim 1 wherein the fiber is comprised of at least 55 atomic percent (at. %) carbon. 